A novel mutation in the CRYAA gene associated with congenital cataract and microphthalmia in a Chinese family.

BACKGROUND: Congenital cataract is the leading cause of blindness in children worldwide. Approximately half of all congenital cataracts have a genetic basis. Protein aggregation is the single most important factor in cataract formation. METHODS: A four-generation Chinese family diagnosed with autosomal dominant congenital cataracts and microphthalmia was recruited at the Shengjing Hospital of China Medical University. Genomic DNA was extracted from the peripheral blood of the participants. All coding exons and flanking regions of seven candidate genes (CRYAA, CRYBA4, CRYBB2, CRYGC, GJA8, MAF, and PITX3) were amplified and sequenced. Restriction fragment length polymorphism (RFLP) assays were performed to confirm the candidate causative variant, c.35G > T in the CRYAA gene. We constructed pcDNA3.1(+)-CRYAA expression plasmids containing either the wild-type or the R12L mutant alleles and respectively transfected them into HEK293T cells and into HeLa cells. Western blotting was performed to determine protein expression levels and protein solubility. Immunofluorescence was performed to determine protein sub-cellular localization. RESULTS: A heterozygous variant c.35G > T was identified in exon 1 of CRYAA, which resulted in a substitution of arginine to leucine at codon 12 (p.R12L). The nucleotide substitution c.35G > T was co-segregated with the disease phenotype in the family. The mutant R12L-CRYAA in HEK293T cells showed a significant increase in the expression level of the CRYAA protein compared with the wild-type cells. Moreover, a large amount of the mutant protein aggregated in the precipitate where the wild-type protein was not detected. Immunofluorescence studies showed that the overexpressed mutant CRYAA in HeLa cells formed large cytoplasmic aggregates and aggresomes. CONCLUSIONS: In summary, we described a case of human congenital cataract and microphthalmia caused by a novel mutation in the CRYAA gene, which substituted an arginine at position 12 in the N-terminal region of αA-crystallin. The molecular mechanisms that underlie the pathogenesis of human congenital cataract may be characterized by the prominent effects of the p.R12L mutation on αA-crystallin aggregation and solubility. Our study also expands the spectrum of known CRYAA mutations.

Novel population specific autosomal copy number variation and its functional analysis amongst Negritos from Peninsular Malaysia.

Copy number variation (CNV) has been recognized as a major contributor to human genome diversity. It plays an important role in determining phenotypes and has been associated with a number of common and complex diseases. However CNV data from diverse populations is still limited. Here we report the first investigation of CNV in the indigenous populations from Peninsular Malaysia. We genotyped 34 Negrito genomes from Peninsular Malaysia using the Affymetrix SNP 6.0 microarray and identified 48 putative novel CNVs, consisting of 24 gains and 24 losses, of which 5 were identified in at least 2 unrelated samples. These CNVs appear unique to the Negrito population and were absent in the DGV, HapMap3 and Singapore Genome Variation Project (SGVP) datasets. Analysis of gene ontology revealed that genes within these CNVs were enriched in the immune system (GO:0002376), response to stimulus mechanisms (GO:0050896), the metabolic pathways (GO:0001852), as well as regulation of transcription (GO:0006355). Copy number gains in CNV regions (CNVRs) enriched with genes were significantly higher than the losses (P value <0.001). In view of the small population size, relative isolation and semi-nomadic lifestyles of this community, we speculate that these CNVs may be attributed to recent local adaptation of Negritos from Peninsular Malaysia.

A novel mutation in the albumin gene (c.1A>C) resulting in analbuminemia.

BACKGROUND: Analbuminemia (OMIM # 103600) is a rare autosomal recessive disorder manifested by the absence or severe reduction of circulating serum albumin in homozygous or compound heterozygous subjects. The trait is caused by a variety of mutations within the albumin gene. DESIGN: We report here the clinical and molecular characterisation of two new cases of congenital analbuminemia diagnosed in two members of the Druze population living in a Galilean village (Northern Israel) on the basis of their low level of circulating albumin. The albumin gene was screened by single-strand conformation polymorphism and heteroduplex analysis, and the mutated region was submitted to DNA sequencing. RESULTS: Both the analbuminemic subjects resulted homozygous for a previously unreported c.1 A>C transversion, for which we suggest the name Afula from the hospital where the two cases were investigated. This mutation causes the loss of the primary start codon ATG for Met1, which is replaced by a - then untranslated - triplet CTG for Leu. (p.Met1Leu). The use of an alternative downstream ATG codon would probably give rise to a completely aberrant polypeptide chain, leading to a misrouted intracellular transport and a premature degradation. CONCLUSIONS: The discovery of this new ALB mutation, probably inherited from a common ancestor, sheds light on the molecular mechanism underlying the analbuminemic trait and may serve in the development of a rapid genetic test for the identification of a-symptomatic heterozygous carriers in the Druze population in the Galilee.

Multiple congenital anomalies-hypotonia-seizures syndrome is caused by a mutation in PIGN.

BACKGROUND: This study reports on a hitherto undescribed autosomal recessive syndrome characterised by dysmorphic features and multiple congenital anomalies together with severe neurological impairment, chorea and seizures leading to early death, and the identification of a gene involved in the pathogenesis of the disease. METHODS: Homozygosity mapping was performed using Affymetrix Human Mapping 250k NspI arrays. Sequencing of all coding exons of the candidate genes was performed with primer sets designed using the Primer3 program. Fluorescence activated cell sorting was performed using conjugated antibody to CD59. Staining, acquisition and analysis were performed on a FACSCalibur flow cytometer. RESULTS: Using homozygosity mapping, the study mapped the disease locus to 18q21.32-18q22.1 and identified the disease-causing mutation, c.2126G→A (p.Arg709Gln), in PIGN, which encodes glycosylphosphatidylinositol (GPI) ethanolamine phosphate transferase 1, a protein involved in GPI-anchor biosynthesis. Arginine at the position 709 is a highly evolutionarily conserved residue located in the PigN domain. The expression of GPI linked protein CD59 on fibroblasts from patients as compared to that in a control individual showed a 10-fold reduction in expression, confirming the pathogenic consequences of the mutation on GPI dependent protein expression. CONCLUSIONS: The abundant expression of PIGN in various tissues is compatible with the diverse phenotypic features observed in the patients and with the involvement of multiple body systems. The presence of developmental delay, hypotonia, and epilepsy combined with multiple congenital anomalies, especially anorectal anomalies, should lead a clinician to suspect a GPI deficiency related disorder.

A Chinese pedigree of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL): clinical and radiological features.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a rare hereditary cerebral vascular disease thought to be confined to Japan. This paper reports a Chinese pedigree of CARASIL in which two patients exhibited all of the typical clinical features of the disease. The radiological features are also discussed and compared with those of CADASIL. These cases illustrate the unique clinical and radiological features of CARASIL and challenge the idea that CARASIL is limited to the Japanese population.

CTG repeats at the myotonic protein kinase gene in a healthy Chilean population sample.

OBJECTIVES: To study the variability at the myotonic dystrophy protein kinase (DMPK) gene in a Chilean sample of healthy people. DM1 is an autosomal dominant disorder caused by an expansion of a (CTG) repeat at the 3'-UTR of the gene DMPK. Healthy individuals have alleles under 35 repeats and diseased individuals have over 50. METHODS: Genotyping the number of (CTG) repeats at this gene in a sample of healthy Chilean people. RESULTS: Allele frequencies were significantly different from those of other populations. The most frequent allele was with five repeats. The frequency of larger alleles (>18 CTG repeats) was 11%, close to the European frequency (12%) and higher than the Japanese (8%) and Aboriginal Pehuenche samples (8%). CONCLUSIONS: Allelic frequencies in the Chilean sample studied were intermediate between those of the two ancestral populations (European and Pehuenche).

Phenotypic spectrum of Fukutinopathy: most severe phenotype of Fukutinopathy.

Fukuyama-type congenital muscular dystrophy (FCMD), Walker-Warburg syndrome (WWS), and muscle-eye-brain (MEB) disease are clinically similar autosomal recessive disorders characterized by congenital muscular dystrophy, cobblestone lissencephaly, and eye anomalies. Among them, WWS is the most severe syndrome. Causative genes for FCMD (Fukutin), WWS (POMT1), and MEB (POMGnT1) have been identified. The vast majority of Japanese FCMD patients carry at least one copy of an ancestral founder insertion mutation. Patients homozygous for this insertion show a milder phenotype than do compound heterozygotes, carrying the insertion in combination with a missense or nonsense mutation on the other allele. No Japanese FCMD patients have been identified with nonfounder mutations on both alleles. A Turkish boy with characteristics of WWS was detected to have a homozygous nonsense mutation in exon 5 of Fukutin. This is the first case worldwide in which a Fukutin mutation has been found outside the Japanese population. Later, another Turkish boy with WWS phenotype was found to have a homozygous nonsense mutation in exon 4 of Fukutin. These two Turkish boys represent the most severe end of the phenotypic spectrum of Fukutin mutations. The Japanese FCMD patients carrying at least one copy of a founder mutation in the noncoding region may produce a lower level of mature Fukutin than normal and generate a relatively mild FCMD phenotype. The homozygous nonsense mutations within the coding region identified in Turkish patients are predicted to cause a total loss of fukutin activity and are likely to produce a more severe phenotype which closely resembles WWS.

[Sequence analysis of OTOF gene in a Chinese pedigree with autosomal dominant auditory neuropathy].

OBJECTIVE: To investigate if the OTOF gene contributes to the non-syndromic hearing loss of a Chinese pedigree with dominantly inherited auditory neuropathy (AN). METHOD: The subjects included were 9 live individuals in an autosomal dominant AN pedigree, 3 sporadic AN patients and 3 normal-hearing controls. Genomic DNA was isolated from the peripheral leukocytes of the subjects using the Pure gene DNA Isolation Kits. Firstly, the whole coding sequence of OTOF gene of one family patient were PCR amplified using specific primers. Each fragment was purified and subsequently analyzed by direct sequencing in an Applied Biosystems 3 730 automated DNA sequencer. The resultant sequence data were compared with the standard sequence to identify deafness-associated mutations. Other DNA samples were then screened for these mutations by PCR amplification and sequence analysis. RESULT: PCR amplifications were successfully conducted in all the subjects. Comparison of the resultant OTOF sequence in one family patient with the standard sequence identified 10 nucleotide variants which do not lead to amino acid change. These mutations were also detectable in other family individuals, 3 sporadic AN patients and 3 normal-hearing controls. CONCLUSION: The OTOF does not seem to contribute to the pathogenesis of this Chinese AN family, which suggest new gene(s) involvement.

Clinical and genetic features in a Chinese pedigree with autosomal dominant auditory neuropathy.

BACKGROUND: A variety of processes and etiologies are thought to be involved in the pathophysiology of auditory neuropathy (AN). However, little is known about the clinical and molecular characteristics of hereditary AN. OBJECTIVE: To explore the clinical and genetic findings of a Chinese family with AN. METHODS: Seven patients in three consecutive generations of the pedigree were selected. Detailed history collection, physical examination, and audiological evaluations including pure-tone audiometry, acoustic immittance, auditory brainstem responses, cochlear microphonics, and evoked otoacoustic emissions, and mitochondrial DNA analysis were performed. RESULTS: All subjects involved are offspring of a female ancestor in the pedigree. In 6 of them, the hearing impairment started before the age of 9. Audiograms showed bilateral, symmetric, and profound deafness. Other audiological examinations revealed absent acoustic reflexes and auditory brainstem responses, and preserved evoked otoacoustic emissions and cochlear microphonics. One subject was characterized by normal audiological findings except high-frequency hearing loss with later onset. Hearing deterioration was found in 2 subjects who were followed for 26 months. Physical examination and mitochondrial DNA analysis yielded normal results. CONCLUSIONS: Clinical features in the pedigree are consistent with type II AN. Pedigree analysis and molecular findings indicate an autosomal dominant inheritance.

Cambodian founder effect for spinocerebellar ataxia type 3 (Machado-Joseph disease).

Four families from the same region of Cambodia immigrated to the Pacific Northwest of the United States. All four families have been discovered to have spinocerebellar ataxia type 3 (SCA 3; Machado-Joseph disease) with a similar clinical phenotype. CAG repeat expansions in the ATXN3 gene range from 72 to 77. Mean age of onset has varied from 19 to 44 years and mean age at death of 4 individuals has been 60 years. The prevalence of the various subtypes of SCA varies worldwide from country to country. Neurologists should be alert to the possibility of SCA 3 in Cambodian patients with unexplained cerebellar ataxia.

Maternal serum biochemistry at 11-13(+6) weeks in relation to the presence or absence of the fetal nasal bone on ultrasonography in chromosomally abnormal fetuses: an updated analysis of integrated ultrasound and biochemical screening.

BACKGROUND: Screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) at 11-13(+6) weeks of gestation is associated with a detection rate of 90%, for a false-positive rate of 5%. Recent evidence suggests that in about 70% of fetuses with trisomy 21 the nasal bone is not visible at the 11-13(+6) week scan and that the frequency of absence of nasal bone differs in different ethnic groups. In addition, there is a relationship between absent nasal bone and nuchal translucency thickness. In a preliminary study we showed that while PAPP-A levels were lower and free beta-hCG levels were higher in trisomy 21 fetuses with an absent nasal bone, this difference was not statistically different. In fetuses with trisomy 13 and trisomy 18, there is also a high (57 and 67%) incidence of an absent nasal bone. The aim of this present study was to extend our examination of whether the level of maternal serum biochemical markers is independent of the presence or absence of the nasal bone in cases with trisomy 21 and to ascertain if any differences exist in cases with trisomies 13 and 18. METHODS: This study data comprised 100 trisomy 21 singleton pregnancies at 11-13(+6) weeks of gestation from our previous study and an additional 42 cases analysed as part of routine OSCAR screening. A total of 34 cases with trisomy 18 and 12 cases with trisomy 13 were also available. Ultrasound examination was carried out for measurement of fetal NT and assessment of the presence or absence of the fetal nasal bone. Maternal serum free beta-hCG and PAPP-A were measured using the Kryptor rapid random access immunoassay analyser (Brahms Diagnostica AG, Berlin). The distribution of maternal serum free beta-hCG and PAPP-A in chromosomally abnormal fetuses with absent and present nasal bone was examined. RESULTS: The nasal bone was absent in 29 and present in 13 of the new trisomy 21 cases and in 98 (69%) and 44 respectively in the combined series. For the trisomy 18 cases, the nasal bone was absent in 19 (55.9%) cases and in 3 (25%) of cases of trisomy 13. There were no significant differences in median maternal age, median gestational age, NT delta, free beta-hCG MoM and PAPP-A MoM in trisomy 21 fetuses with and without a visible nasal bone, and similarly for those with trisomies 13 or 18. For a false-positive rate of 5%, it was estimated that screening with the four markers in combination with maternal age would be associated with a detection rate of 96% of cases with trisomy 21. For a false-positive rate of 0.5%, the detection rate was 88%. CONCLUSIONS: There is no relationship between an absent fetal nasal bone and the levels of maternal serum PAPP-A or free beta-hCG in cases with trisomies 13, 18 or 21. An integrated sonographic and biochemical test at 11-13(+6) weeks can potentially identify about 88% of trisomy 21 fetuses for a false-positive rate of 0.5%.

PARK6-linked autosomal recessive early-onset parkinsonism in Asian populations.

The authors performed linkage analysis in 39 families with autosomal recessive early-onset PD (AR-EOPD) negative for parkin and DJ-1 mutations. Eight families including three Japanese, two Taiwanese, one Turkish, one Israeli, and one Philippine showed evidence of linkage with PARK6 with multipoint log of the odds (lod) score of 9.88 at D1S2732. The results indicate worldwide distribution of PARK6-linked parkinsonism.

Is there a 'Basque' profile regarding autosomal recessive deficiencies of coagulation factors?

When excluding haemophilia and von Willebrand disease, coagulation factors deficiencies constitute rare autosomal recessive disorders (<1 in 500,000) of less precisely defined epidemiology. We have reported herein the distribution of these entities in the French Basque Country, a genetic isolate of very old individualization with peculiar biological specificities. The prevalence of these disorders was markedly high, especially, as already shown, factor XI deficiency. This unusual profile needs to be discussed in the view of population genetics.

[Consanguinity and congenital abnormalities]. / Konsangvinitet og medfødte misdannelser.

Knowledge of consanguinity is relevant for employees in the Danish national health service, since about 7.5% of the Danish population has another ethnic background than Danish and the majority comes from cultures where consanguineous marriages are not unusual. In the literature it is found that consanguineous couples have a higher risk of having children with congenital malformations. The risk is increased by a factor 2 to 2 1/2. The average risk in Denmark is about 3%. Primarily, the autosomal recessive diseases are expressed in children with consanguineous parents. In order to advise and diagnose it is essential to clarify the consanguinity state. In case of pregnancy with consanguineous parents, we recommend: 1) Counselling to estimate the risk of foetal illness and information about possible examination possibilities. 2) An ultrasound scan at the gestational age of 11-14 weeks in order to measure nuchal translucency and an early malformation scan. 3) An ultrasound scan for malformations at the gestational age of 18-20 weeks. 4) An ultrasound scan especially in order to detect foetal heart malformations at the gestational age of 20-24 weeks.