Pseudodominance of lipoprotein lipase (LPL) deficiency due to a nonsense mutation (Tyr302>Term) in exon 6 of LPL gene in an Italian family from Sardinia (LPL(Olbia))

We analyzed the molecular defect in the lipoprotein lipase (LPL) gene of a young boy from Sardinia who had primary hyperchylomicronemia, pancreatitis, and a complete LPL deficiency in post-heparin plasma. Analysis of LPL gene was performed by using single strand conformation polymorphism (SSCP) and direct sequencing of SSCP-positive region. The proband was homozygous for a C > A transversion in exon 6, which converts the codon for tyrosine at position 302 into a termination codon and eliminates an RsaI restriction site; this allowed the rapid screening of the proband's family members, among whom nine heterozygotes and one additional homozygote were identified. The homozygote was the proband's paternal grandmother who had shown the first clinical manifestation (recurrent pancreatitis) of LPL deficiency at the age of 54 years. LPL mutation carriers showed a mild dyslipidemic phenotype characterized by a reduction of high density lipoprotein-cholesterol (HDL-C) levels, HDL-C/total cholesterol ratio, and low density lipoprotein (LDL) size, associated with a variable increase of triglyceride levels. Five of these carriers were also heterozygotes for beta-thalassemia (Q39X mutation). In these double mutation carriers, plasma HDL-C levels were higher and plasma triglycerides tended to be lower than in carriers of LPL mutation alone. The Tyr302 > Term mutation encodes a truncated protein of 301 amino acids that is probably not secreted by the LPL producing cells. This is the first mutation of LPL gene found in Sardinians.     

Novel diagnostic approach to citrin deficiency: analysis of citrin protein in lymphocytes

Citrin deficiency induces two clinical features; namely neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) and adult-onset type II citrullinemia. Hypercitrullinemia is the most characteristic feature, whereas there are non-citrullinemic individuals. Diagnosis of citrin deficiency is performed by genetic analysis, although the 12 known mutations in the alleles are not detected in about 15% of cases. Thus, we aimed to examine citrin protein in lymphocytes isolated from peripheral blood as an alternative diagnostic method. We examined 38 children having an episode of cholestatic liver dysfunction, 8 heterozygotes, and 11 healthy individuals. All subjects were evaluated for citrin protein by Western blotting and for the 12 known mutations by gene analysis. Citrin protein was detected in 15 of 38 children with cholestatic liver dysfunction. Fourteen of them were negative for 12 known mutations in both alleles, whereas one patient was found to have a known mutation in one allele. Citrin protein was absent in 23 of the 38 patients. Among these 23, gene analysis diagnosed citrin deficiency in 19, whereas 2 patients were later revealed to be NICCD with novel mutations. In the remaining 2 patients, who exhibit the clinical features of NICCD, a known mutation was detected in one allele but no mutation was identified in another allele. Citrin protein was also detected in the 8 heterozygotes and 11 healthy individuals. We disclosed that citrin was deficient in lymphocytes among patients with citrin deficiency. Analysis of citrin is useful to diagnose citrin deficiency even in patients without known mutations or hypercitrullinemia.     

A fetal fatty-acid oxidation disorder as a cause of liver disease in pregnant women.

BACKGROUND: Acute fatty liver of pregnancy and the HELLP syndrome (hemolysis, elevated liver-enzyme levels, and a low platelet count) are serious hepatic disorders that may occur during pregnancy in women whose fetuses are later found to have a deficiency of long-chain 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase. This enzyme resides in the mitochondrial trifunctional protein, which also contains the active site of long-chain 2,3-enoyl-CoA hydratase and long-chain 3-ketoacyl-CoA thiolase. We undertook this study to determine the relation between mutations in the trifunctional protein in infants with defects in fatty-acid oxidation and acute liver disease during pregnancy in their mothers. METHODS: In 24 children with 3-hydroxyacyl-CoA dehydrogenase deficiency, we used DNA amplification and nucleotide-sequence analyses to identify mutations in the alpha subunit of the trifunctional protein. We then correlated the results with the presence of liver disease during pregnancy in the mothers. RESULTS: Nineteen children had a deficiency only of long-chain 3-hydroxyacyl-CoA dehydrogenase and presented with hypoketotic hypoglycemia and fatty liver. In eight children, we identified a homozygous mutation in which glutamic acid at residue 474 was changed to glutamine. Eleven other children were compound heterozygotes, with this mutation in one allele of the alpha-subunit gene and a different mutation in the other allele. While carrying fetuses with the Glu474Gln mutation, 79 percent of the heterozygous mothers had fatty liver of pregnancy or the HELLP syndrome. Five other children, who presented with neonatal dilated cardiomyopathy or progressive neuromyopathy, had complete deficiency of the trifunctional protein (loss of activity of all three enzymes). None had the Glu474Gln mutation, and none of their mothers had liver disease during pregnancy. CONCLUSIONS: Women with acute liver disease during pregnancy may have a Glu474Gln mutation in long-chain hydroxyacyl-CoA dehydrogenase. Their infants are at risk for hypoketotic hypoglycemia and fatty liver.     

Aldolase B mutations in Italian families affected by hereditary fructose intolerance.

Hereditary fructose intolerance (HFI) is an inborn error of metabolism caused by aldolase B deficiency. The aldolase B gene has been cloned and the following mutations causing HFI have been identified: A149P (a G----C transversion in exon 5), A174D (a C----A transversion in exon 5), L288 delta C (a base pair deletion in exon 8), and N334K (a G----C transversion in exon 9). We have investigated the occurrence of these mutations in 11 Italian patients affected by HFI using PCR and hybridisation to specific oligomers. We found that four patients were homozygous for the A149P mutation, two patients were homozygous for the A174D mutation, three patients were compound heterozygotes for both the A149P and A174D mutations, one patient was homozygous for the N334K mutation, and one patient did not show any of the reported mutations (HFI diagnosis carried out by aldolase B assay). The L288 delta C mutation has not been found in this survey.     

Double mutation (A171T) and (D444H) is a common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States

Biotinidase deficiency is inherited as an autosomal recessive trait that, unless treated with pharmacologic doses of biotin, can result in neurologic and cutaneous symptoms. We have identified two new mutations in exon D of the biotinidase gene of children with profound biotinidase deficiency ascertained by newborn screening. Transition 511G→A near the 5′ end of exon D results in a substitution of threonine for alanine171 (A171T) and transversion 1330G→C occurs close to the 3′ end of exon D causing a substitution of histidine for aspartic acid 444 (D444H). The D444H mutation was detected in four individuals from our normal population whose mean serum biotinidase activity is 5.25 nmol/min/ml, which is significantly lower than the mean normal activity (7.1 nmol/min/ml). We calculated that this mutation causes a 52% loss of activity in the aberrant enzyme. Twenty-three individuals with the D444H mutation were found by allele specific oligonucleotide analysis of DNA from 296 randomly-selected, anonymous dried-blood spots. We estimate the frequency of this allele in the general population to be 0.039. In contrast, no individuals in 376 have the A171T mutation. Fourteen children (eleven probands and three siblings) out of 31 enzyme-deficient children have both the A171T and D444H mutations. Both mutations are inherited from a single parent as a double mutation allele. The nine families in which this allele was identified are of mostly European ancestry, although the mutation cannot be attributed to a specific nationality or ethnic group. The serum of a child who is homozygous for the double mutation allele has very little CRM and the aberrant enzyme has very low biotinyl-hydrolase activity and no biotinyl-transferase activity. This double mutation allele (A171T and D444H) is a common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States. Hum Mutat 11:410, 1998. © 1998 Wiley-Liss, Inc.     

Short stature in carriers of recessive mutation causing familial isolated growth hormone deficiency

Isolated growth hormone deficiency (IGHD) IB is an autosomal recessive disorder characterized by a good response to exogenous growth hormone (GH) treatment without development of anti-GH antibodies. Patients with IGHD IB were found to be compound heterozygotes for deletion and frameshift mutations as well as homozygotes for splicing mutations in the GH-1 gene. Recently, a novel splicing mutation in the GH-1 gene was identified in an extended, consanguineous Arab-Bedouin family from Israel with IGHD IB. Prior to the identification of this mutation, a considerable number of children with short stature in this family were found normal on pharmacological stimulation for GH release. This observation prompted a genotype/phenotype correlation of potential heterozygotes in the family. Carriers of the mutant GH-1 allele were found as a group to have a significantly shorter stature than normal homozygote (mean standard deviation scores, 1.67 and -0.40, respectively, P<0.05). Moreover, 11 of 33 (33%) heterozygotes, but only 1 of 17 (5.9%) normal homozygotes, had their height at 2 or more SD below the mean. Overall, 48.5% of studied heterozygotes were found to be of appreciably short stature with height at or lower than the 5th centile (> or = -1.7 SD), whereas only 5.9% of the normal homozygotes did (P<0.004). This phenomenon of heterozygotes for a recessive mutation in the GH-1 gene manifesting short stature, might imply that some such mutations may account for non-GH deficiency reduced height in the general population.     

Double mutation (A171T and D444H) is a common cause of profound biotinidase deficiency in children ascertained by newborn screening the the United States. Mutations in brief no. 128. Online

Biotinidase deficiency is inherited as an antosomal recessive trait that, unless treated with pharmacologic doses of biotin, can result in neurologic and cutaneous symptoms. We have identified two new mutations in exon D of the biotinidase gene of children with profound biotinidase deficiency ascertained by newborn screening. Transition 511G->A near the 5' end of exon D results in a substitution of threonine for alanine 171 (A171T) and transversion 1330G->C occurs close to the 3' end of exon D causing a substitution of histidine for aspartic acid 444 (D444H). The D444H mutation was detected in four individuals from our normal population whose mean serum biotinidase activity is 5.25 nmol/min/ml, which is significantly lower than the mean normal activity (7.1 nmol/min/ml). We calculated that this mutation causes a 52% loss of activity in the aberrant enzyme. Twenty-three individuals with the D444H mutation were found by allele specific oligonucleotide analysis of DNA from 296 randomly-selected, anonymous dried-blood spots. We estimate the frequency of this allele in the general population to be 0.039. In contrast, no individuals in 376 have the A171T mutation. Fourteen children (eleven probands and three siblings) out of the 31 enzyme-deficient children have both the A171T and D444H mutations. Both mutations are inherited from a single parent as a double mutation allele. The nine families in which this allele was identified are of mostly European ancestry, although the mutation cannot be attributed to a specific nationality or ethnic group. The serum of a child who is homozygous for the double mutation allele has very little CRM and the aberrant enzyme has very low biotinylhydrolase activity and no botinyl-transferase activity. This double mutation allele (A171T and D444H) is a common cause of profound biotinidase deficience in children ascertained by newborn screening in the United States.     

Mutations in BTD causing biotinidase deficiency

Biotinidase (BTD) is the only enzyme that can cleave biocytin, a product of the proteolytic digestion of holocarboxylases. Profound BTD deficiency (less than 10% mean normal activity in serum) is an autosomal recessive disorder that can result in neurological and cutaneous abnormalities. Both the cDNA and the genomic DNA of normal BTD gene have been isolated and characterized. The BTD gene is localized to chromosome 3p25. Thus far 61 mutations in three of the four exons of the BTD and one mutation in an intron gene that cause profound BTD deficiency have been reported. Mutations occur at different frequencies in symptomatic children than they do in children ascertained by newborn screening. Two mutations, 98‐104del7ins3 and R538C, were present in 52% or 31 of 60 alleles found in symptomatic patients. Three other mutations, A755G, Q456H, and 511 G>A; 1330G>C (double mutation), accounted for 52% of the alleles detected by newborn screening in the United States. Two asymptomatic adults, parents of children with profound BTD deficiency detected by newborn screening, have been described. Additional different mutations have been found in Turkish, Saudi Arabian, and Japanese children with profound BTD deficiency. Partial BTD deficiency (10–30% of mean normal serum activity) is predominantly caused by the single 1330G>C mutation that results in D444H on one allele in combination with one of the mutations causing profound deficiency on the other allele. Four intragenic polymorphisms, three neutral and one amino acid change, have also been found. Although a preponderance of mutations causing the production of truncated BTD protein occurs in symptomatic children with profound deficiency, preliminary studies fail to demonstrate clear genotype–phenotype correlations. Hum Mutat 18:375–381, 2001. © 2001 Wiley‐Liss, Inc.     

Mutational spectrum in German patients with phenylalanine hydroxylase deficiency

We report on the spectrum and frequency of mutations in the phenylalanine hydroxylase (PAH) gene in 226 German families with PAH deficiency, most of them from Southern Germany. A total of 88 mutations were identified in 428 out of 438 mutant PAH alleles including one novel stop mutation L293X (c.878T>A). In three families, two phenylketonuria (PKU) mutations were found in cis, and in one family a de novo mutation was observed. A comparison of the results from Southern Germany with those of other parts of Western Germany showed no obvious local mutation clustering. In addition we studied the genotypic spectrum of 39 Turkish families with PAH deficiency. Twenty-three mutations were identified in 73 out of 75 Turkish chromosomes including two novel mutations: E280A (c.839A>G) in Exon 7 and IVS10-7C>A (c.1066-7C>A) in Intron 10. A new polymorphism IVS4+47C/T (c.441+47C>T) was found in mutant and normal PAH alleles. Screening of 170 German and 150 Turkish individuals without family history of PAH deficiency revealed 10 and 12 heterozygotes, respectively, a higher frequency of carriers than expected. A novel mutations of uncertain functional relevance, R169H (c.506G>A) in Exon 5 was found in two Turkish heterozygotes. Most of the Turkish heterozygotes carried mild mutations, indicating that mild forms of PAH deficiency may be more common in that population than previously recognised.     

Molecular characterization of Complement Factor I deficiency in two Spanish families

Complement Factor I (CFI) is a regulator of the classical and alternative pathways. CFI has enzymatic activity and is able to cleave C3b and C4b. Homozygous Factor I deficiency is associated with infectious and/or autoimmune diseases.

Here we describe the biochemical and genetic characterization in two Spanish families with complete Factor I deficiency. In Family 1, the propositus suffered from several episodes of meningitis for more than a year. Biochemical complement studies showed undetectable Factor I levels in the propositus and in her sister, while their parents and a brother had partial Factor I deficiency and were healthy. In Family 2, three out of five children were homozygous for Factor I deficiency, two of whom suffered from meningitis and the third one from several infections. The parents and the other two siblings were healthy and heterozygous for Factor I deficiency.

Molecular studies showed that the two families had different mutations at exon 5 of the Factor I gene, which codifies for module LDLr1. One mutation corresponds to a 772G>A change at the donor splice site that was originally found in a family from Northern England. The second is a new missense mutation 739T>G, that generates a Cys to Gly change.     

Molecular defects of the C7 gene in two patients with complement C7 deficiency

Different genetic mutations have been described in complement components resulting in total or subtotal deficiency states. In this work we report the genetic basis of C7 deficiency in a previously reported Spanish patient exhibiting a combined total deficiency of C7 and C4B associated with systemic lupus erythematosus. Exon-specific polymerase chain reaction and sequencing revealed a not previously described single base mutation in exon 10 (T1458A) leading to a stop codon that causes the premature truncation of the C7 protein (C464X). Additionally, a C to A transversion at position 1561 (exon 11) was found in the patient resulting in an amino acid change (R499S). This latter mutation has been previously reported in individuals with subtotal C7 deficiency or with combined subtotal C6/C7 deficiency from widely spaced geographical areas. Another novel mutation was found in a second patient with meningococcal meningitis of Bolivian and Czech origin; a 11-base pair deletion of nucleotides 631-641 in exon 6 leading to the generation of a downstream stop codon causing the premature truncation of the C7 protein product (T189 x 193). This patient was found to be a heterozygous compound for another mutation in C7; a two-base pair deletion of nucleotides 1922 and 1923, 1923 and 1924 or 1924 and 1925 in exon 14 (1922delAG/1923delGA/1924delAG), leading again to the generation of a downstream stop codon that provokes the truncation of the C7 protein (S620x630). This latter mutation has been recently reported by our group in another Spanish family. Our results provide more evidences for the heterogeneous molecular basis of C7 deficiency.     

Nonspecific interstitial pneumonia and usual interstitial pneumonia with mutation in surfactant protein C in familial pulmonary fibrosis.

Nonspecific interstitial pneumonia, a recently described form of idiopathic interstitial pneumonia, is characterized by uniform involvement of the alveolar septae with interstitial inflammation and variable amounts of fibrosis. Histological observations differentiate nonspecific interstitial pneumonia from usual interstitial pneumonia and clinically, patients with a nonspecific interstitial pneumonia pattern show better prognosis than those with usual interstitial pneumonia. We have genetically analyzed a family with a history of usual interstitial pneumonia. Most of the patients presented as adults and their biopsies showed a pattern consistent with usual interstitial pneumonia. However, three family members presented in early childhood and their biopsies revealed a nonspecific interstitial pneumonia pattern. The inheritance pattern of usual interstitial pneumonia is consistent with autosomal dominant inheritance with variable expression. DNA sequence analyses of the surfactant protein C gene in children with nonspecific interstitial pneumonia and adults with usual interstitial pneumonia exhibit a common heterozygous mutation located in exon 5. The mutation causes a Leu188 to Gln188 change in the carboxy-terminal region of prosurfactant protein C, possibly affecting peptide processing. These observations suggest that individuals with this particular mutation in surfactant protein C gene might be at increased risk of interstitial lung disease of variety of types.     

A Novel Mutation in a Patient with a Deficiency of the Eighth Component of Complement Associated with Recurrent Meningococcal Meningitis

Introduction  Complement component C8 is one of the five terminal complement components required for the formation of the membrane attack complex. Complete absence of C8 results in increased susceptibility to gram-negative bacteria such as Neisseria species. Materials and Methods  Two functionally distinct C8 deficiency states have been described: C8 α–γ deficiency has been predominantly reported amongst Afro-Caribbeans, Hispanics, and Japanese and C8β mainly in Caucasians. Results  We report a case of functional and immunochemical deficiency of the complement component C8, diagnosed in a Caucasian adult following three episodes of meningitis. Western blotting and hemolytic assay demonstrated absence of C8β. In genetic studies, the common exon 9 C > T transition responsible for 85% of C8β deficiencies was not found. Two mutations were identified: a novel duplication mutation, c.1047_1053 dupGGCTGTG in exon 7 that introduces a frame shift, resulting in the addition of seven novel amino acid residues and a premature stop codon, and a previously reported mutation, c.271C > T in exon 3. The parents each expressed one of these mutations, confirming compound heterozygosity. Discussion  This is the first report of a duplication mutation in C8β deficiency and extends the molecular heterogeneity of the disorder.     

Identification of a second "French Canadian" LDL receptor gene deletion and development of a rapid method to detect both deletions

Hobbs et al. (N. Engl. J. Med. 317: 734-737, 1987) reported a large deletion of approximately 10 kilobases in the 5' portion of the human low-density lipoprotein (LDL) receptor gene. This deletion affects about 60% of familial hypercholesterolemia (FH) heterozygotes in the French Canadian population. We have developed a rapid, convenient method for the detection of the deletion using double digestion with the restriction enzymes XbaI and EcoRV, or triple digestion with XbaI, EcoRV and XmnI, and a 650 bp cDNA probe, radio-labeled using a random oligonucleotide primer technique. Eighty French Canadian FH heterozygotes were screened for the presence of the deletion. Forty-seven (59%) of them were found to carry the 10 kb deletion. Using the same method, we also identified a new mutation which was found in four of the 80 (5%) FH patients. This mutation has been found to be a 5 kb deletion removing exons 2 and 3 of the LDL receptor gene, which correspond to the first two repeats of the LDL receptor binding domain. Cosegregation of the 5 kb deletion and the FH phenotype was observed in one family. Possible structure-function relationship is discussed.     

Glucose-6-phosphatase gene (727G→T) splicing mutation is prevalent in Hong Kong Chinese patients with glycogen storage disease type la

Glycogen storage disease type la (GSD1a) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase (GóPase). We analyzed the GóPase genes of two unrelated Chinese families with GSD1a. DNA sequencing of all five exons and the exonintron boundaries revealed a G → T transversion at nucleotide 727 (727G→T) in exon 5, which has previously been reported to cause abnormal splicing. In one family, the subject and her affected sister were confirmed to be homozygous for this mutation and their parents to be heterozygotes. In the other family, the proband was identified to be heterozygous for this mutation, and a novel mutation, the 341delG in exon 2, was identified. This mutation alters the reading frame and creates a stop codon TAA 15 codons downstream from the mutation, resulting in a truncated protein. Family studies revealed that the father was heterozygous for the 727G → T mutation and that the mother was heterozygous for the 341delG mutation. This is the first time that the 727G→T mutation has been found in Chinese patients or outside Japan. Since we only tested two GSDla families and found 727G→T in both, we believe that this mutation may also be prevalent in our local Chinese population. To investigate allele frequencies, we screened 385 Chinese healthy volunteers and found two asymptomatic carriers. Our findings suggest that the 727G → T mutation is indeed prevalent in Hong Kong.     

Molecular basis of lipoamide dehydrogenase deficiency in Ashkenazi Jews

We studied 13 patients with lipoamide dehydrogenase (LAD) deficiency, originating from seven Ashkenazi Jewish families. Their disease was characterized by recurrent attacks of vomiting, abdominal pain, and encephalopathy accompanied by elevated liver transaminases, prolonged prothrombin time, and occasionally associated with lactic and ketoacidemia or with myoglobinuria. Two patients who presented neonatally suffered from residual neurological damage with attention deficit hyperactive disorder, mild ataxia, motor incoordination, muscle hypotonia, and weakness. Nine patients who presented in early childhood or later suffered from exertional fatigue between decompensation episodes but were otherwise asymptomatic. Two patients died because of intractable metabolic acidosis and multi-organ failure. In all patients LAD activity was reduced to 8 to 21% of the control in muscle or lymphocytes. In four patients LAD protein in muscle was reduced to 20 to 60% of the control. Direct sequencing of the cDNA of the LAD gene showed that 12 of the 14 mutated alleles carried the G229C mutation and two carried an insertion mutation 105insA (Y35X). The patients who presented neonatally and had more severe sequelae were compound heterozygotes for the two mutations; patients who presented in early childhood or later were homozygous for the G229C mutation. Using an allele-specific oligonucleotide hybridization technique, nine heterozygotes for the G229C mutation were identified among 845 anonymous individuals of Ashkenazi Jewish origin disclosing a carrier rate of 1:94. Because of the significant morbidity associated with the disease, screening for the G229C mutation among Ashkenazi Jewish couples should be considered. Am. J. Med. Genet. 82:177–182, 1999. © 1999 Wiley-Liss, Inc.     

Contribution of the CFTR gene, the pancreatic secretory trypsin inhibitor gene (SPINK1) and the cationic trypsinogen gene (PRSS1) to the etiology of recurrent pancreatitis

Acute recurrent/chronic pancreatitis (CP) is a complex multigenic disease. This is a case-control study consisting of 25 Greek patients with CP and a control population of 236 healthy Greek subjects. The whole coding area and neighboring intronic regions of the three genes were screened. Seventeen of 25 patients (68%) had mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene: nine compound heterozygotes with either mild or severe mutations and eight heterozygotes. Four patients (16%) carried CFTR-modulating haplotypes V470-TG11-T5 and V470-TG12-T7. All were negative for PRSS1 gene mutations, while variants c.486C/T and c.738C/T were found in nine patients each, three homozygotes for the minor alleles. Two carried SPINK1 gene mutation p.N34S, one being transheterozygote with CFTR mutation p.F1052V. The promoter variant -253T>C was found in four individuals (one homozygous for the minor allele), all four being transheterozygotes with mutations in the CFTR gene as well. Finally two carried c.272C/T in the 3' untranslated region, one being a p.N34S carrier as well. In total, 80% (20/25) of patients had a molecular defect in one or both of the CFTR and SPINK1 genes, suggesting that mutations/variants in the CFTR plus or minus mutations in the SPINK1, but not the PRSS1 gene, may confer a high risk for recurrent pancreatitis.     

Clinical Variability of Family Members with the C104R Mutation in Transmembrane Activator and Calcium Modulator and Cyclophilin Ligand Interactor (TACI)

Purpose

Common Variable Immunodeficiency Disorder (CVID) is a complex disorder that predisposes patients to recurrent and severe infections. The C104R mutation in the transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) is the most frequent mutation identified in patients with CVID. We carried out a detailed immunological and molecular study in a family with a C104R mutation.

Methods

We have undertaken segregation analysis of a kindred with C104R mutations of the TACI gene. Detailed immunological and molecular investigations were carried out for this kindred and the clinical phenotype was compared to the genotype.

Results

Segregation analysis of our kindred showed that inheriting single or double copy of the C104R mutation does not consign an individual to CVID. All heterozygotes in the family were phenotypically different, ranging from asymptomatic to ill-health. A family member with a wild type TACI variant had CVID-related phenotype including IgA deficiency and type 1 diabetes. Interestingly, a family member with the homozygous C104R/C104R variant did not meet the criteria for CVID because he had excellent, albeit unsustained, vaccine responses to T cell dependent and T cell independent vaccine antigens despite profound hypogammaglobulinemia.

Conclusion

The C104R mutation does not correlate with the clinical phenotypes in this family.     

Complement component C7 deficiency in two Spanish families

Different genetic mutations have been described in complement component C7 deficiency, a molecular defect clinically associated with an increased susceptibility to neisserial recurrent infections. In this work we report the genetic basis of C7 deficiency in two different Spanish families (family 1 and family 2). In family 1, of Gypsy ethnical background, exon-specific polymerase chain reaction and sequencing revealed a not previously described single base deletion of nucleotide 1309 (exon 10) in the patient, as well as in her father, leading to a stop codon that causes the premature truncation of the C7 protein (K416 X 419). Additionally, the patient and her mother displayed a missense mutation at position 1135 (exon 9) located in the first nucleotide of the codon GGG (CGG), resulting in a change of amino acid (G357R). This mutation was firstly described in individuals of Moroccan Sephardic Jewish ancestry and has been also reported among Spaniards. In family 2, another novel mutation was found in homozygosity in two siblings; a two base-pair deletion of nucleotides 1922 and 1923 in exon 14 leading to the generation of a downstream stop codon causing the truncation of the C7 protein product (S620 X 630). Our results provide more evidence for the heterogeneous molecular basis of C7 deficiency as well as for the subsequent susceptibility to meningococcal disease, since different families carry different molecular defects. On the other hand, certain C7 defects appear to be prevalent in individuals from certain populations or living in defined geographical areas.     

Mutation 985A>G in the MCAD gene shows low incidence in Estonian population

Medium-chain acyl-CoA dehydrogenase (MCAD) is an enzyme responsible for large part of mitochondrial beta-oxidation of fatty acids and therefore stays on key position of cellular energy supply. In case of its deficiency, starvation, rapid growth periods or infections may cause fatal lack of energy, especially in the first years of life. MCAD deficiency is inherited in an autosomal recessive manner and it has been shown to be rather common in some European countries (Great Britain 1 in 6,000, Switzerland 1 in 10,000). In Caucasoid populations one mutation, the 985A>G transition, causing the amino acid substitution K329E, accounts for about 90% of all mutant MCAD alleles. Here we present data about screening the Estonian population for this mutation. We analyzed the DNA from 1,098 persons from all regions of Estonia (all newborns born in one month) and found 5 heterozygotes for 985A>G, that makes the carrier frequency 1 in 220 and the frequency of possibly affected homozygotes 1 out of 193,000. No mutant alleles were found among the samples of the children, who had unclear diagnosis for death during the years 1994 and 1995.