Haplotypes identified by 10 DNA restriction fragment length polymorphisms at the human low density lipoprotein receptor gene locus.

Ten useful two allele restriction fragment length polymorphisms of the low density lipoprotein receptor gene were used for haplotype analysis in 45 unrelated familial hypercholesterolaemic (FH) patients, 60 normal controls, and 32 FH homozygotes, all of whom were white Afrikaners. Pedigree analysis in 27 informative heterozygous FH and 23 normal families has shown the segregation of at least 17 haplotypes in the normal population (111 chromosomes) compared to a predominant association of two of these haplotypes with the disease in the FH subjects. This association was further confirmed in 32 FH homozygotes, indicating at least two 'founder' members for the disease in the Afrikaner population. Recombination events were not detected in any of the families studied and we thus conclude that the haplotypes associated with FH function as specific markers for the disease and will allow presymptomatic diagnosis in affected families.     

我国Marfan综合征基因连锁标记的研究

为了探索对Ｍａｒｆａｎ综合征进行产前诊断和症状前诊断的方法，应用１５号染色体ＦＢＮ１基因内两个多态位点ＴａｑⅠ限制性片段长度多态性（ＲＦＬＰ）和（ＴＡＡＡＡ）ｎ扩增片段长度多态性（Ａｍｐ－ＦＬＰ）为遗传标记，在正常人群中检出前者有５．０ｋｂ（＋）和６．０ｋｂ（－）两种等位基因，基因频率各为２７％和７３％；后者有１５０ｎｔ（１）和１６０ｎｔ（２）两种等位基因，基因频率分别为３１％和６９％，未见白种人中的罕见变异型。两个患病家系的单倍型分离分析表明，致病基因均与－，２单倍型连锁，提示中国人群中Ｍａｒｆａｎ综合征也与ＦＢＮ１基因连锁。以该基因内的多态位点为遗传标记，可对该病的一些家系成员进行产前或症状前诊断。     

Multiplex family-based study in systemic lupus erythematosus: association between the R620W polymorphism of PTPN22 and the FcgammaRIIa (CD32A) R131 allele

A functional polymorphism in PTPN22, a gene encoding a phosphatase involved in T-cell signaling, has been associated with autoimmunity. We checked for the prevalence of the PTPN22 R620W polymorphism in multiplex families affected with systemic lupus erythematosus (SLE) and other autoimmune diseases. Its association with other polymorphisms in mannose binding lectin (MBL) and FcgammaRIIa (CD32A) genes was also studied. Deoxyribonucleic acid samples were obtained from 233 Spanish individuals who belonged to 21 families in which at least two members had been diagnosed with some autoimmune disease, mainly SLE. A healthy control population was also included (n= 129). Genotyping for the R620W single-nucleotide polymorphism (SNP) was performed by restriction fragment length polymorphism analysis of polymerase chain reaction products. Allele frequency for the T allele was slightly higher in the families with autoimmune disease, especially when considering the affected individuals (0.094 vs 0.062). Actually, 18.8% affected family members vs 11.6% controls had the polymorphism (P= 0.179). Nineteen percent of affected individuals had both the PTPN22 T and the CD32A R131 alleles, whereas only 8.5% unaffected relatives had both susceptibility alleles simultaneously [P= 0.031, odds ratios 2.508 (95% confidence interval 1.066-5.896)]. The tendency toward finding the T allele more frequently in members affected with some particular autoimmune disorder suggests that this SNP may confer susceptibility to autoimmunity. The fact that more affected than unaffected relatives carried both the T and the R131 alleles simultaneously leads us to think about the existence of a combinatorial effect between genes that could help define individuals prone to autoimmune diseases.     

Genetic analysis of adult-onset cataract in a city-based ophthalmic hospital

Adult-onset cataract (AOC) is a major ocular health problem and is the number one cause of blindness in the world. It is interesting to note that if the development of cataract is delayed by 10 years, the number of cataract surgeries needed would decrease by 45%. To prevent or delay cataract, the molecular pathological mechanisms underlying the lens change have to be understood, and this requires that the genes involved in such mechanisms should be identified. Hence, in this study we aim to identify AOC families which show a clear mendelian inheritance pattern, as only these families would be ideal for mapping the genes responsible. Over a period of 8 months, from September 1995—April 1996, 17 families with two or more affected members were identified. Segregation analysis showed autosomal dominant inheritance in multiple affected families. We propose to map the genes responsible for cataract in these families by linkage analysis and mutational screening of candidate genes.     

TGFBI基因相关的Thiel-Behnke角膜营养不良家系的建立者效应分析

目的 对2个Thiel-Behnke角膜营养不良的家系进行基因诊断和建立者效应分析.方法 提取家系A中15名成员(13例患者,2名健康成员)、家系B中14例成员(6例患者,8名健康成员)以及20名健康自愿者的基因组DNA,通过DNA测序检测转化生长因子β诱导基因(transforming growth factor beta induced,TGFBI/BIGH3)的突变,并对2个家系成员进行单倍型分析.结果 所有患者TGFBI基因的第12外显子发生R555Q突变,2个家系成员具有部分相同的单倍型.结论 基因检测有助于Thiel-Behnke角膜营养不良的确诊.2个患病家系可能来自于同一祖先.     

Sex ratios of affected and transmitting members of multiple case families with neural tube defects.

In order to study the genetic aspects of the relation between neural tube defects and sex, we selected families with at least two closely related affected members. The sex ratios of both affected and normal transmitting persons were determined in these multiple case families. Our results indicate that there is a relation between the position of the lesion in the spine and sex. Furthermore, the affected persons in one family show significant concordance for sex as shown by the analysis of families with just two affected members. To our surprise, the group of normal transmitters appears to consist of significantly more females than males. This is in contrast to similar families with non-syndromic cleft lip +/- palate, where males predominate both among affected persons and normal transmitters. Finally, affected females most often inherited the predisposition to a neural tube defect from their mother. The possible role of inherited factors is discussed.     

Identification of an expanded CAG repeat in the Huntington''s disease gene (IT15) in a family reported to have benign hereditary chorea.

Benign hereditary chorea (BHC) is a rare autosomal dominant disorder characterised by the onset of non-progressive chorea in childhood and the absence of cognitive impairment. Using primers flanking the (CAG)n repeat in IT15, expansion of which is associated with HD, we have detected an abnormal PCR product in four affected members from one family where affected subjects were originally reported to have BHC. The expanded allele contains 38 repeats in the affected parent and this undergoes further enlargement to 39 and 45 repeats in the two affected offspring. We conclude that the diagnostic criteria for BHC should include a normal result from analysis for the (CAG)n expansion identified in HD.     

The substitution of Arg for Gly2433 in the human skeletal muscle ryanodine receptor is associated with malignant hyperthermia

Single strand conformations! polymorphism analysis was usedto screen exons 43 and 44 In the skeletal muscle ryanodlne receptorgene from 17 positively diagnosed members of families in whichchromosome 19–1 Inked malignant hyperthermla (MH) wassegregating. A polymorphism In two unrelated Individuals wasfound to result from the substitution of A for G7297, leadingto the substitution of Arg for Gly²⁴³³ .This mutation Is adjacentto a mutation (Arg²⁴³⁴ to His) previously linked to MH and centralcore disease (Y.Zhang et al., Nature Genet 1993, 5, 46–50).Subsequent screening showed the presence of the mutation infour of 106 MH families tested and Its absence from about 1000other chromosomes. The mutation was present In all six individualsIn four families who had had an MH reaction, in two obligatecarriers and in 10 Individuals diagnosed as MH susceptible bythe caffeine/halothane contracture test (CHCT). The mutationwas present In an Individual with a normal response to the CHCTand was absent in three individuals with a positive CHCT response.These discrepancies would be consistent with inaccuracies inthe CHCT and/or with segregation of a second MH allele withintwo of the four affected families.     

Who is a carrier? Detection of unsuspected mutations in 21-hydroxylase deficiency

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is a common autosomal-recessive disorder. During our routine genotyping of affected individuals and their relatives using allele-specific oligonucleotide hybridization and single-strand conformational polymorphism analysis, we identified two families each segregating three mutations. In both families, a mutation known to be associated with 21-hydroxylase deficiency was identified in healthy individuals but was not detected in the propositus. The propositus in family 1 was shown to be a homozygous carrier for G at nucleotide 655, which alters the splice acceptor site at exon 3. The propositus in family 2 carried the same splicing mutation on the maternal allele and a gene deletion/conversion on the paternal allele. In both families, other clinically unaffected relatives carried the Q318X mutation in exon 8. If molecular diagnostic studies had been limited to the mutation carried by the propositi, relatives would have been misinformed regarding their status as carriers or mildly affected individuals. The findings in these two families emphasize the high frequency of alleles causing 21-hydroxylase deficiency in the population. © 1996 Wiley-Liss, Inc.     

Novel spastin mutations and their expression analysis in two Italian families

Mutations in spastin cause the most common form of pure autosomal dominant hereditary spastic paraparesis (SPG4). Here, we report two Italian families affected with SPG4-linked HSP harboring two novel spastin mutations. SSCP/sequencing analysis of the spastin gene showed a single base pair deletion causing a frame-shift in one family (1442delT) and a missense mutation (1726T>C) resulting in a leucine to proline amino-acid change (L534P) in the other family. Total RNA from the mutant and the wild-type spastin allele in muscle biopsies from patients from the two affected families was quantitated. RNA expression was almost absent from the spastin allele harboring the single base pair deletion, while it was nearly normal for the spastin allele harboring the missense mutation. These data suggest that varying spastin RNA levels are found in out-of-frame and missense spastin mutations and imply different mechanisms involved in the molecular pathology of SPG4 linked HSP.     

A Cys634Gly substitution of the RET proto-oncogene in a family with recurrence of multiple endocrine neoplasia type 2A and cutaneous lichen amyloidosis

Germ-line mutations of the RET proto-oncogene, involving five cysteine residues at codons 609, 611, 618, 620 and 634, are associated with two variants of the inherited cancer syndrome multiple endocrine neoplasia type 2: type 2A and familial medullary thyroid carcinoma. The association of multiple endocrine neoplasia type 2A with the dermatological disorder cutaneous lichen amyloidosis has already been reported, and mutations in the Cys634 have been identified in different families. We describe here an additional pedigree in which multiple endocrine neoplasia type 2A and cutaneous lichen amyloidosis cosegregate. A Cys634Gly was identified by direct sequencing of the RET proto-oncogene exon 11 in the affected individuals. The mutation creates a new HaeIII site, and restriction analysis performed on all family members rules out the presence of the altered allele in two children and consequently the risk of developing thyroid tumors. These results emphasize the role of molecular analysis of the RET proto-oncogene in diagnosing presymptomatically those individuals at risk of inheriting the disease allele.     

Mutation screening of all 65 exons of the fibrillin-1 gene in 60 patients with Marfan syndrome: Report of 12 novel mutations

Mutations in the fibrillin-1 gene on chromosome 15q21.1 have been found to cause Marfan syndrome, a dominantly inherited disorder characterised by clinically variable skeletal, ocular, and cardiovascular abnormalities. In this study we screened all 65 exons of the fibrillin-1 gene in 20 Marfan syndrome families where at least two affected individuals were characterised and available for analysis, another 30 families with only one affected member available for analysis, and in 10 sporadic cases. In large well-characterised families with more than four affected individuals, the detection rate for mutations rose to 78% (7/9), in families with either two or three affected members 27% (3/11). In families where only one affected family member was available, the mutation detection rate was 17% (5/30), and in sporadic cases it was 20% (2/10). In addition, we found eight neutral polymorphisms. Twelve of the 17 disease-causing mutations identified have not been previously described, thus raising the total number of different fibrillin-1 mutations reported to 85 in 94 unrelated cases. Hum Mutat 10:280–289, 1997. © 1997 Wiley-Liss, Inc.     

Isolated congenital anosmia with morphologically normal olfactory bulb in two Iranian families: a new clinical entity?

Congenital total loss of the sense of smell occurs as a part of a syndrome or isolated anosmia. Kallmann syndrome is the most well known congenital anosmia associated with hypogonadotropic hypogonadism. Isolated congenital anosmia (ICA) is a very rare condition and appears to be due to changes in the olfactory epithelium or to aplasia of the olfactory nerve, bulb, and tract. Here we report two unrelated Iranian families with ICA. One family consisted of nine affected members, and the other family contained three affected members. Clinical history, physical examination, and smell testing by intravenous injection of combined vitamins (Alinamin trade mark, Takeda Pharmaceutical Co. Ltd., Japan) confirmed the disease in each affected member. No signs of hypogonadism or other neurological disorders were observed in any affected members. Family analysis with the complete ascertainment method under assumption of the same condition in the two families suggested that the disease is not inconsistent with an autosomal dominant mode with incomplete penetrance. The inheritance in one family appears unusual, i.e., there were no affected individuals in the third generation. When only two upper generations in the family are concerned, the segregation ratio was 0.39 +/- 0.11. Male-to-male transmissions were observed and both sexes were affected in both families. Magnetic resonance imaging (MRI) of the olfactory bulb and sulcus revealed no evidence of morphological changes in all affected members, suggesting that these patients have either a defect in the olfactory epithelium or a functional defect in the olfactory cortex.     

Familial non-Hodgkin lymphoma: histologic diversity and relation to other cancers.

Familial non-Hodgkin lymphoma (NHL) cases were classified according to the histologic criteria (modified) of Rappaport, to determine the extent of morphologic similarities of the tumors. In four families affected members had different tumor histologies that may be observed in an individual patient as the lymphoma progresses. In two families, the affected relatives had tumors of seemingly discordant histology. These tumors may nonetheless be etiologically related as indicated by the pattern of laboratory abnormalities, especially immunologic, in affected as well as unaffected members. The 20 cases had a reversal of the sex ratio (M/F) usually seen in NHL: 0.5 instead of 1.3. Other tumors observed in these families included primary hepatocellular carcinoma, pulmonary adenocarcinoma, Hodgkin disease, and acute lymphocytic leukemia - all of which have been associated with inborn or acquired immunodeficiency states.     

Familial non-Hodgkin lymphoma: Histologic diversity and relation to other cancers

Familial non-Hodgkin lymphoma (NHL) cases were classified according to the histologic criteria (modified) of Rappaport, to determine the extent of morphologic similarities of the tumors. In four families affected members had different tumor histologies that may be observed in an individual patient as the lymphoma progresses. In two families, the affected relatives had tumors of seemingly discordant histology. These tumors may nonetheless be etiologically related as indicated by the pattern of laboratory abnormalities, especially immunologic, in affected as well as unaffected members. The 20 cases had a reversal of the sex ratio (M/F) usually seen in NHL: 0.5 instead of 1.3. Other tumors observed in these families included primary hepatocellular carcinoma, pulmonary adenocarcinoma, Hodgkin disease, and acute lymphocytic leukemia - all of which have been associated with inborn or acquired immunodeficiency states.     

七个成人型多囊肾病家系基因的诊断

应用ＰＫＤ１两侧四种探针（３’ＨＶＲ、ＰＧＧＧ１和另一侧的２４－１、２１８ＥＰ６），通过Ｓｏｕｔｈｅｒｎ印迹杂交、ＲＦＬＰ连锁分析，对成人型多囊肾病进行基因诊断的研究。在７个ＡＰＫＥ家系共４１个成员中，进行了基因单体型分析，１６个ＡＰＫＤ患者的ＲＦＬＰ单体型被证明与ＰＫＤ１基因相连锁，检测出６个症状前个体，发现２个重组体，结果表明用ＰＫＤ１两旁侧基因探针进行联合分析，可极有效地检出重组体，避免误诊，提高诊断的准确性。     

Maternal - offspring HLA-DRB1 compatibility in multiple sclerosis

Major histocompatibility complex (MHC) compatibility has been reported to facilitate the long-term tolerance of fetal or maternally derived stem cells exchanged during pregnancy. Furthermore, such compatibility has been suggested to play a role in fetal viability. An increase in maternal - fetal human leukocyte antigen (HLA) compatibility for class II DR alleles has previously been observed in the autoimmune disease scleroderma. Here, we examined the hypothesis that increased maternal - fetal MHC class II DR compatibility was associated with multiple sclerosis (MS) risk. HLA-DRB1 typing was performed in 2170 affected individuals and 2894 unaffected relatives from 1006 families with MS in at least two members. We found no evidence for increased HLA compatibility between affected individuals and their mothers, compared with unaffected individuals and their mothers, nor compared with affected individuals and their fathers. We also observed no excess of homozygosity of mothers compared with fathers of individuals with MS. In families in which the father shared exactly one allele with the mother, we found no excess in transmission of this allele to affected or unaffected offspring. These findings do not support a role for an excess maternal - fetal HLA-DRB1 compatibility in MS susceptibility.     

Mutations in connexin31 underlie recessive as well as dominant non-syndromic hearing loss

Mutations in the GJB3 gene encoding connexin31 (Cx31) can cause a dominant non-syndromic form of hearing loss (DFNA2). To determine whether mutations at this locus can also cause recessive non-syndromic deafness, we screened 25 Chinese families with recessive deafness and identified in two families affected individuals who were compound heterozygotes for Cx31 mutations. The three affected individuals in the two families were born to non-consanguineous parents and had an early onset bilateral sensorineural hearing loss. In both families, differing SSCP patterns were observed in affected and unaffected individuals. Sequence analysis in both families demonstrated an in-frame 3 bp deletion (423-425delATT) in one allele, which leads to the loss of an isoleucine residue at codon 141, and a 423A-->G transversion in the other allele, which creates an Ile-->Val substitution at codon 141 (I141V). Neither of these two mutations was detected in DNA from 100 unrelated control subjects. The altered isoleucine residue lies within the third conserved alpha-helical transmembrane domain (M3), which is critical for the formation of the wall of the gap junction pore. Both the deletion of the isoleucine residue 141 and its substitution to valine in the two families could alter the structure of M3, and impair the function of the gap junction. The present data demonstrate that, like mutations in connexin26, mutations in Cx31 can lead to both recessive and dominant forms of non-syndromic deafness.     

Hereditary non-polyposis colorectal cancer (HNPCC): phenotype-genotype correlation between patients with and without identified mutation

Affected members of hereditary non-polyposis colorectal cancer (HNPCC) families develop colorectal cancer at an early age (mean 45 yr) and frequently get extracolonic cancers particularly in the uterus, urinary tract, and small intestine. They have a high risk of developing more than one primary colorectal cancer if not treated with subtotal colectomy at first operation and have more frequent right-sided colon cancers and less frequent rectum cancers, compared to patients with sporadic colorectal cancer. We have screened 31 families fulfilling the Amsterdam criteria and 54 families with a colorectal cancer clustering but not fulfilling the Amsterdam criteria for mutations in MLH1 and MSH2 by direct sequencing, and detected a mutation in 61% of the Amsterdam positive families but only in 15% of the Amsterdam negative families. Genotype-phenotype correlation was compared between 141 affected individuals with an identified mutation and 78 affected individuals from Amsterdam positive families in which a mutation was not identifiable in MLH1 or MSH2. In the affected persons with identified mutations, all expected phenotypic traits were represented, whereas affected persons in whom no mutation was detected fell into two clearly distinguishable subgroups. The minor subgroup, in which no mutation was identified, generally had the same characteristics as found in affected persons with identified mutations. The major subgroup differed significantly in clinical features and exhibited phenotypic traits similar to those found in late-onset families, including abundance of rectal cancer, few HNPCC-related cancers, lower frequency of multiple colorectal cancers, and later age at onset. Finally, for six missense mutations and one single codon deletion, the pathogenic potential was evaluated by domain localization, lod score calculation or segregation analysis when possible, and mutation-induced biochemical change. The results indicate that the majority of missense mutations are pathogenic, although further characterization by functional assays is necessary before implementation in predictive testing programs.     

Study of HLA segregation in 479 thalassemic families

479 families, each with a proband affected by homozygous beta-thalassemia, were typed for HLA. 224 families with a total of 1020 members were typed for the HLA-A, B, C, DR and DQ loci and 255 families with 1046 family members, were typed for the HLA-A, B, and C loci. Altogether, 896 A, B, C, DR and DQ haplotypes and 1020 A, B and C haplotypes were defined. At the same time, 120 healthy unrelated individuals from the same population were typed and used as controls. The analysis of the results was carried out at antigen, allele, haplotype, genotype and sex ratio level with the aim of looking on the one hand, for the existence of heterogeneity between the probands, the unrelated individuals and the healthy siblings and, on the other, for the existence of any distortion whatsoever of the HLA segregation in either the probands or in the healthy siblings in respect of the expected values according to the Mendelian equilibrium. No significant differences were evident between the probands and the controls by the tests carried out at different levels of the HLA system. This leads us to exclude the existence of an association between beta-thalassemia and HLA in the population studied. Moreover, the analysis of the transmission of the alleles, the haplotypes, the genotypes and the sex-ratio by parents to both affected and to healthy children did not show any clear evidence of segregation distortion in respect of the theoretical values.