A novel compound heterozygous mutation in the thyroglobulin gene resulting in congenital goitrous hypothyroidism with high serum triiodothyronine levels

Thyroglobulin abnormality is a rare cause of congenital hypothyroidism and only a limited number of mutations in the thyroglobulin gene have been reported. We analyzed the thyroglobulin gene in a patient with congenital goitrous hypothyroidism. This girl was identified with hyperthyrotropinemia in a neonatal mass-screening test. The patient had goiter, and her body weight gain was poor. Distal femoral epiphysis was absent on roentgenography. Her serum thyroxine level was low; however, her triiodothyronine level was high. Autoantibodies against triiodothyronine, thyroid peroxidase, and thyroglobulin were all negative. Her serum thyroglobulin level was undetectable. The thyroglobulin gene from the genomic DNA of the patient was analyzed by direct sequencing. Two novel heterozygous missense mutations, Cys1897Tyr (exon 31) and Arg2336Gln (exon 40), were found in the patient. The former mutation was derived from her mother, suggesting a compound heterozygous state. Normal triiodothyronine and low thyroxine concentrations are often observed in patients with thyroglobulin gene mutations. We considered that some patients with thyroglobulin abnormality might have high triiodothyronine levels. In cases of congenital goitrous hypothyroidism with normal-to-high triiodothyronine levels and low serum thyroglobulin levels, thyroglobulin abnormality should be considered.     

Homozygous TREM2 mutation in a family with atypical frontotemporal dementia

TREM2 mutations were first identified in Nasu-Hakola disease, a rare autosomal recessive disease characterized by recurrent fractures because of bone cysts and presenile dementia. Recently, homozygous and compound heterozygous TREM2 mutations were identified in rare families with frontotemporal lobar degeneration (FTLD) but without bone involvement. We identified a p.Thr66Met heterozygous mutation in a new consanguineous Italian family. Two sibs had early onset autosomal recessive FTLD without severe bone disorders. Atypical signs were present in this family: early parietal and hippocampus involvement, parkinsonism, epilepsy, and corpus callosum thickness on brain magnetic resonance imaging. This study further demonstrates the implication of TREM2 mutations in FTLD phenotypes. It illustrates the variability of bone phenotype and underlines the frequency of atypical signs in TREM2 carriers. This and previous studies evidence that TREM2 mutation screening should be limited to autosomal recessive FTLD with atypical phenotypes characterized by: (1) a very young age at onset (20–50 years); (2) early parietal and hippocampal deficits; (3) the presence of seizures and parkinsonism; (4) suggestive extensive white matter lesions and corpus callosum thickness on brain magnetic resonance imaging.     

一例火棉胶婴儿TGM1基因新的复合杂合性突变鉴定

目的 鉴定1例火棉胶婴儿转谷氨酰胺酶1基因(transglutaminase 1,TGM1)的致病性突变.方法 提取患儿及其父母的外周血DNA,PCR扩增TGM1基因的编码及剪切位点序列,对PCR产物进行直接测序.同时检测100名无血缘关系的正常人作为对照.用TGM1邻近的微卫星标记在家系中构建单倍型以确定突变的来源.应用CLUSTAL X(1.81)软件分析突变氨基酸的跨种属保守性.结果 患儿携带了TGM1的两个复合杂合性突变:c.420A＞G (I140M)及c.832G＞A (G278R),均为国际上未报道过的新突变.两个错义突变均造成了TGM1蛋白内高度保守区的氨基酸置换.突变c.420A＞G (I140M)遗传自父亲,位于蛋白的转谷氨酰胺酶N功能域;突变c.832G＞A (G278R)遗传自母亲,位于野生蛋白的转谷氨酰胺酶N功能域和转谷氨酰胺酶样功能域之间.两个突变在100名无血缘关系的正常人中均未发现.结论 c.420A＞G (I140M)和c.832G＞A (G278R)复合杂合性突变为该患儿的致病性突变,本研究结果为该病的诊断提供了分子学依据.     

Heterozygous TREM2 mutations in frontotemporal dementia

A causative association was recently demonstrated between homozygous TREM2 mutations and frontotemporal dementia (FTD)-like syndrome and between heterozygous TREM2 exon2 genetic variations and late-onset Alzheimer's disease (AD). The objective of this study was to evaluate whether heterozygous TREM2 genetic variations might be associated to the risk of FTD. TREM2 exon 2 was sequenced in a group of 1030 subjects—namely, 352 patients fulfilling clinical criteria for FTD, 484 healthy control subjects (HCs), and 194 patients with AD. The mutation frequency and the associated clinical characteristics were analyzed. We identified 8 missense and nonsense mutations in TREM2 exon 2 in 24 subjects. These mutations were more frequent in patients with FTD than in HCs (4.0% vs. 1.0%, p = 0.005). In particular, TREM2 Q33X, R47H, T66M, and S116C mutations were found in FTD and were absent in HCs. These mutations were associated with either the semantic variant of primary progressive aphasia or the behavioral variant FTD phenotypes. The FTD and AD groups were not significantly different with regard to TREM2 genetic variation frequency (AD: 2.6%, p = 0.39). Heterozygous TREM2 mutations modulate the risk of FTD in addition to increasing susceptibility to AD. Additional studies are warranted to investigate the possible role of these mutations in the pathogenesis of neurodegenerative disorders.     

Novel N-terminal domain mutation in prion protein detected in 2 patients diagnosed with frontotemporal lobar degeneration syndrome

Prion protein gene mutations have been associated with clinical pictures mimicking neurodegenerative diseases different from inherited prion diseases (IPD). We report a novel missense P39L mutation in the N-terminal domain of prion protein in 2 patients affected by frontotemporal lobar degeneration syndrome, negative for mutations in genes causative of dementia. Neither the first carrier, a 67-year-old male in which the onset was a progressive non-fluent aphasia, nor the second carrier, a 78-year-old male affected by frontotemporal dementia and parkinsonism, showed any clinical or instrumental findings suggestive of IPD. Genetic screening of healthy controls and in silico analysis provide support for the potential pathogenicity of this variant. Patient phenotypes, unclassifiable as prion disease, may depend on the location of the mutation in the N-terminal domain, outside the amyloid core of pathologic prion protein, although further functional studies are required to determine whether and how this mutation exerts its pathogenic effect. However, genetic screening of prion protein gene becomes relevant in familial degenerative dementia, particularly in geographical areas with high IPD prevalence.     

Understanding phenotype variability in frontotemporal lobar degeneration due to granulin mutation

Phenotype in patients with granulin (GRN) mutations is unpredictable, ranging from behavioral variant frontotemporal dementia (bvFTD) to agrammatic variant of primary progressive aphasia (avPPA). To date the wide clinical variability of FTLD-GRN remains unexplained. The aim of the study was to identify genetic pathways differentiating phenotypic expression in patients carrying GRN mutations. Patients carrying the same GRNT272SfsX10 mutation were enrolled, a careful clinical assessment was carried out, and the diagnosis of either bvFTD (n = 10, age = 63.9 ± 9.4) or avPPA (n = 6, age = 58.8 ± 4.7) was done. Microarray gene expression analysis on leukocytes was performed. Genes differentially expressed between the groups were validated by real time polymerase chain reaction considering an age-matched healthy controls group (n = 16, age = 58.4 ± 10.7). We further considered a group of FTD with no GRN mutations (GRN-) (n = 21, 13 bvFTD, and 8 avPPA) for comparisons. Real-time polymerase chain reaction (PCR) confirmed a significant decrease in leukocytes mRNA messenger RNA (mRNA) levels of RAP1GAP in bvFTD patients as compared with avPPA (p = 0.049). This finding was specific for patients with GRN mutations, as we did not observe this pattern in FTD GRN-patients (p = 0.99). The alteration of RAP1GAP mRNA levels may explain the clinical variability of GRN-FTLD patients. This is the first report linking a molecular pathway to specific phenotype expression in FTLD-GRN. To understand the clinical relevance of our early results it will be mandatory to extend the observation to other clinical and neuropathological series.     

A family with two female siblings with compound heterozygous FMR1 premutation alleles

Premutation alleles (55–200 CGG repeats) of the fragile X mental retardation (FMR1) gene have been linked to various types of clinical involvement ranging from mood and anxiety disorders to immunological disorders and executive function deficits. Carrier females typically have a premutation allele and a normal allele (<55 CGG repeats). Although rare, seven cases of females that carry two expanded alleles (compound heterozygous premutation) have been reported. Here, we report on four members of a family including two compound heterozygous premutation sisters with similar CGG allele sizes, affected with different levels of clinical severity.     

Founder effect and estimation of the age of the Progranulin Thr272fs mutation in 14 Italian pedigrees with frontotemporal lobar degeneration

Progranulin (PGRN) mutations have been recognized to be monogenic causes of frontotemporal lobar degeneration (FTLD). PGRN Thr272fs mutation in the Italian population has been previously identified. In the present study, we evaluated the occurrence of a founder effect studying 8 polymorphic microsatellite markers flanking the PGRN gene in 14 apparently unrelated families. We identified a common haplotype associated with PGRN Thr272fs carriers, assuming common ancestry. The inferred age analysis (range between 260 [95% credible set: 227-374] and 295 [95% credible set: 205-397] generations) places the introduction of the mutation back to the Neolithic era when the Celts, the population of that period, settled in Northern Italy. PGRN Thr272fs mutation appears to be as either behavioral frontotemporal dementia (80%) or primary progressive aphasia (20%), it was equally distributed between male and female, and the mean age at onset was 59.6 ± 5.9 (range 53-68). In 14 families, autosomal dominant pattern of inheritance was present in 64.2% of cases. No clinical predictors of disease onset were demonstrated. The identification of a large cohort of frontotemporal lobar degeneration (FTLD) patients with homogeneous genetic background well may be used in the search of disease modulators to elucidate genotype-phenotype correlations of progranulopathies.     

A rare heterozygous TREM2 coding variant identified in familial clustering of dementia affects an intrinsically disordered protein region and function of TREM2

Rare coding variants in the triggering receptor expressed on myeloid cells‐2 (TREM2) gene have been associated with Alzheimer disease (AD) and homozygous TREM2 loss‐of‐function variants have been reported in families with monogenic frontotemporal‐like dementia with/without bone abnormalities. In a whole‐exome sequencing study of a family with probable AD‐type dementia without pathogenic variants in known autosomal dominant dementia disease genes and negative for the apolipoprotein E (APOE) ε4 allele, we identified an extremely rare TREM2 coding variant, that is, a glycine‐to‐tryptophan substitution at amino acid position 145 (NM_018965.3:c.433G>T/p.[Gly145Trp]). This alteration is found in only 1 of 251,150 control alleles in gnomAD. It was present in both severely affected as well as in another putatively affected and one 61 years old as yet unaffected family member suggesting incomplete penetrance and/or a variable age of onset. Gly145 maps to an intrinsically disordered region (IDR) of TREM2 between the immunoglobulin‐like and transmembrane domain. Subsequent cellular studies showed that the variant led to IDR shortening and structural changes of the mutant protein resulting in an impairment of cellular responses upon receptor activation. Our results, suggest that a p.(Gly145Trp)‐induced structural disturbance and functional impairment of TREM2 may contribute to the pathogenesis of an AD‐like form of dementia.     

A novel compound heterozygous TACI mutation in an autosomal recessive common variable immunodeficiency (CVID) family

Common variable immunodeficiency (CVID) is a primary immune disorder characterized by low immunoglobulin serum levels and increased susceptibility to infections. Underlying genetic causes are only known in less than 15% of patients and encompass mutations in the genes encoding for ICOS, TACI, BAFF-R, CD19, CD20, CD81 and MSH5. TACI is the most frequently mutated gene among CVID patients. We report on two pediatric Italian male siblings with hypogammaglobulinemia and recurrent respiratory and gastrointestinal infections in association with a novel compound heterozygous TACI mutation. Both patients carry the I87N/C104R mutation that has not been reported yet. This results in aberrant TACI expression and abrogates APRIL binding on EBV B cells. This study identifies a novel combined mutation in TNFRSF13B increasing the spectrum of TACI mutations associated with CVID.     

Severe amygdala dysfunction in a MAPT transgenic mouse model of frontotemporal dementia

Frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) is a neurodegenerative tauopathy caused by mutations in the tau gene (MAPT). Individuals with FTDP-17 have deficits in learning, memory, and language, in addition to personality and behavioral changes that are often characterized by a lack of social inhibition. Several transgenic mouse models expressing tau mutations have been tested extensively for memory or motor impairments, though reports of amygdala-dependent behaviors are lacking. To this end, we tested the rTg4510 mouse model on a behavioral battery that included amygdala-dependent tasks of exploration. As expected, rTg4510 mice exhibit profound impairments in hippocampal-dependent learning and memory tests, including contextual fear conditioning. However, rTg4510 mice also display an abnormal hyperexploratory phenotype in the open-field assay, elevated plus maze, light-dark exploration, and cued fear conditioning, indicative of amygdala dysfunction. Furthermore, significant tau burden is detected in the amygdala of both rTg4510 mice and human FTDP-17 patients, suggesting that the rTg4510 mouse model recapitulates the behavioral disturbances and neurodegeneration of the amygdala characteristic of FTDP-17.     

Artery tortuosity syndrome exhibiting early‐onset emphysema with novel compound heterozygous SLC2A10 mutations

We report on a 2‐year‐old Japanese boy with early‐onset pulmonary emphysema, exhibiting dysmorphic face, loose skin, and inguinal and Morgagni hernias. He was admitted to our hospital owing to refractory respiratory infection. On the basis of his clinical features, we investigated the SLC2A10 gene and identified novel compound heterozygous mutations of c.417T > A and c.692G > A, leading to the diagnosis of artery tortuosity syndrome (ATS). This syndrome is an extremely rare autosomal recessive disorder characterized by tortuosity and elongation of the large and medium‐sized arteries, hyperextensible skin, and diverse hernias, mostly reported from Europe and Middle Eastern countries, but not from Asia. Although chronic obstructive pulmonary disease, namely, emphysema, has not been well documented in ATS, it may be likely because TGF‐beta up‐regulation is known to be evoked by SLC2A10 mutations, resulting in reconstruction of pulmonary endothelial cells and emphysema. This is the first report of ATS associated with early‐onset pulmonary emphysema, suggesting that patients with ATS may also require close attention for chronic obstructive pulmonary disease. © 2013 Wiley Periodicals, Inc.     

Expansion mutation in C9ORF72 does not influence plasma progranulin levels in frontotemporal dementia

A hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9ORF72) gene has recently been described as a cause of familial and sporadic frontotemporal lobar degeneration. The aim of this study was to assess whether plasma progranulin (GRN) levels could be modulated by the presence of this repeat expansion. Sixty-five patients diagnosed with frontotemporal dementia and 10 family members with familial aggregation of disease were screened for the presence of the hexanucleotide repeat expansion in C9ORF72 gene, using a repeat-primed polymerase chain reaction method. Plasma GRN levels were measured in all subjects through enzyme-linked immunosorbent assay. Seven individuals with the repeat expansion were identified. No differences were found between C9ORF72 repeat expansion carriers and noncarriers (116.4 ± 21 ng/mL and 131.7 ± 36 ng/mL, respectively, p = 0.3). Analysis of family members did not disclose any difference in plasma GRN levels between carriers and noncarriers. In conclusion, plasma GRN levels are not influenced by the hexanucleotide repeat expansion in C9ORF72 gene, and therefore, cannot be used as a reliable biomarker to detect mutation carriers.     

A novel heterozygous mutation of three consecutive nucleotides causing Apert syndrome in a Congolese family

Apert syndrome (OMIM 101200) is a rare genetic condition characterized by craniosynostosis and syndactyly of hands and feet with clinical variability. Two single nucleotides mutations in the linker region between the immunoglobulin-like domains II and IIIa of the ectodomainin the Fibroblast Growth Factor Receptor 2 gene (FGFR2, OMIM 176943) are responsible of the vast majority of cases: c.755C > G; p.Ser252Trp (65%) and c.758C > G; p.Pro253Arg (34%. Three exceptional cases carry multiple substitutions of adjacent nucleotides in the linker region.Here we present a Congolese male patient and his mother, both affected with Apert syndrome of variable severity, carrying a previously undescribed heterozygous mutation of three consecutive nucleotides (c.756_758delGCCinsCTT) in the IgII–IgIIIa linker region. This is the fourth live-born patient to carry a multiple nucleotide substitution in the linker region and is the second alternative amino acid substitutions of the Pro253. Remarkably, this novel mutation was detected in the first Central African patient ever to be tested molecularly for the Apert syndrome. To discriminate between a hitherto unreported mutation and an ethnic specific polymorphism, we tested 105 Congolese controls, and no variation was detected.     

Epidemiology and genetics of frontotemporal dementia: a door-to-door survey in Southern Italy

The objectives of this study were to estimate frontotemporal dementia (FTD) prevalence, identify FTD-related mutations, and correlate FTD phenotype with mutations in a Southern Italian population. The study population consisted of subjects ≥ 50 years of age residing in the Community of Biv. on January 1, 2004, and a door-to-door 2-phase design was used. Genetic and biochemical analyses were done on samples collected from 32 patients. Prevalence rates were 0.6 for Alzheimer's disease, 0.4 for vascular dementia (VD), 3.5 for FTD, 0.2 for Parkinson dementia, and 1.2 for unspecified dementia. Three GRN (1 known and 2 novel) mutations with reduced plasma protein levels were found associated to 3 distinct phenotypes (behavioral, affective, and delirious type). We report an unusually high FTD prevalence in the investigated population, but a low prevalence of Alzheimer's disease. We confirm the heterogeneity of FTD phenotype associated with different GRN mutations.     

No evidence of linkage to chromosome 9q21-22 in a Swedish family with frontotemporal dementia and amyotrophic lateral sclerosis

Frontotemporal dementia (FTD) is a neurodegenerative disorder, sometimes occurring together with amyotrophic lateral sclerosis (ALS) within the same family. Recently, a region on chromosome 9q21–22 was reported to harbour a locus that may participate in both disorders [Hosler, B.A., et al., JAMA., 284 (2000) 1664-1669]. In the present study, a Swedish pedigree with both ALS and FTD segregating in the family was investigated by linkage analysis with five markers on chromosome 9q21–22. The pedigree included 17 individuals in two generations, with five affected cases available for analysis. As two-point logarithm of odds scores close to zero were obtained for all markers tested, the region on chromosome 9q21–22 is suggested to be excluded as candidate region in this Swedish FTD/ALS family. Our conclusion is therefore that additional loci involved in these two disorders must be operating.     

Successful pharmacological management of a child with compound heterozygous familial hypercholesterolemia and review of the recent literature

Severe familial hypercholesterolemia (SFH) is characterized by markedly elevated low-density lipoprotein cholesterol (LDL-C) and severe early-onset cardiovascular disease if left untreated. We report on the decade-long therapeutic journey of a 15-year-old boy with SFH due to a severe compound heterozygous genotype. He presented at the age of 5 years with widespread xanthomas and LDL-C of 17.4 mmol/L. He was diagnosed with SFH, initially treated with colestyramine that was subsequently combined with simvastatin. At the age of 12 years, he was diagnosed to have supravalvular aortic stenosis and ezetimibe/atorvastatin was introduced in place of colestyramine/simvastatin. At the age of 14 years, he received triple therapy with evolocumab, initially at the recommended dose of 420 mg monthly and then reduced to 140 mg biweekly. Currently at the age of 15 years, he is on atorvastatin 40 mg ON, ezetimibe 10 mg OM, and evolocumab 140 mg biweekly, achieving LDL-C levels of 2.4 mmol/L. Genetic testing identified compound heterozygous mutations in the LDL receptor genes [c.(940 + 1_941-1) (1845 + 1_1846-1)dup] and exon 12, nucleotide c.1747 C > T, amino acid p.(His583Tyr). Medical management without lipoprotein apheresis can achieve target LDL-C in children with SFH. Our patient, who developed supravalvular aortic stenosis at the age of 12 years, needed early aggressive treatment when SFH guidelines and newer drugs for young children were unavailable. Our patient demonstrated that 140 mg biweekly of evolocumab has the same cholesterol-lowering effect as the recommended 420 mg monthly dose.