Brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome (OMIM 609945): case report and review of the literature

Brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome (OMIM 609945) is a rare congenital disorder. Only seven patients have been reported to date, and the etiology of this syndrome is unknown. Autosomal dominant inheritance with variable expression has been suggested based on the presence of minor features in some parents and the fact that neither parental consanguinity nor pairs of affected siblings were observed. We report on the first patient with this syndrome who was born to consanguineous parents. Neither the mother nor the father, who were first cousins, had clinical features suggestive of a manifestation of brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome. The patient had no siblings, and the family history was unremarkable. Clinical problems included brachydactyly of hands and feet, splaying of fingers and toes, preaxial polydactyly of feet, bilateral tibial aplasia, shortened radius and ulna, and characteristic facial dysmorphic signs. The detailed description of this patient adds to our knowledge of the clinical manifestations of brachyphalangy, polydactyly and tibial aplasia/hypoplasia syndrome and will eventually also contribute to the elucidation of the underlying gene defects.

Genetic male infertility and mutation of CATSPER ion channels

A clinically significant proportion of couples experience difficulty in conceiving a child. In about half of these cases male infertility is the cause and often genetic factors are involved. Despite advances in clinical diagnostics ∼50% of male infertility cases remain idiopathic. Based on this, further analysis of infertile males is required to identify new genetic factors involved in male infertility. This review focuses on cation channel of sperm (CATSPER)-related male infertility. It is based on PubMed literature searches using the keywords 'CATSPER', 'male infertility', 'male contraception', 'immunocontraception' and 'pharmacologic contraception' (publication dates from January 1979 to December 2009). Previously, contiguous gene deletions including the CATSPER2 gene implicated the sperm-specific CATSPER channel in syndromic male infertility (SMI). Recently, we identified insertion mutations of the CATSPER1 gene in families with recessively inherited nonsyndromic male infertility (NSMI). The CATSPER channel therefore represents a novel human male fertility factor. In this review we summarize the genetic and clinical data showing the role of CATSPER mutation in human forms of NSMI and SMI. In addition, we discuss clinical management and therapeutic options for these patients. Finally, we describe how the CATSPER channel could be used as a target for development of a male contraceptive.

A clinical and molecular genetic study of 112 Iranian families with primary microcephaly

BACKGROUND

Primary microcephaly (MCPH) is a genetically heterogeneous disorder showing an autosomal recessive mode of inheritance. Affected individuals present with head circumferences more than three SDs below the age- and sex-matched population mean, associated with mild to severe mental retardation. Five genes (MCPH1, CDK5RAP2, ASPM, CENPJ, STIL) and two genomic loci, MCPH2 and MCPH4, have been identified so far.

METHODS AND RESULTS

In this study, we investigated all seven MCPH loci in patients with primary microcephaly from 112 Consanguineous Iranian families. In addition to a thorough clinical characterisation, karyotype analyses were performed for all patients. For Homozygosity mapping, microsatellite markers were selected for each locus and used for genotyping. Our investigation enabled us to detect homozygosity at MCPH1 (Microcephalin) in eight families, at MCPH5 (ASPM) in thirtheen families. Three families showed homozygosity at MCPH2 and five at MCPH6 (CENPJ), and two families were linked to MCPH7 (STIL). The remaining 81 families were not linked to any of the seven known loci. Subsequent sequencing revealed eight, 10 and one novel mutations in Microcephalin, ASPM and CENPJ, respectively. In some families, additional features such as short stature, seizures or congenital hearing loss were observed in the microcephalic patient, which widens the spectrum of clinical manifestations of mutations in known microcephaly genes.

CONCLUSION

Our results show that the molecular basis of microcephaly is heterogeneous; thus, the Iranian population may provide a unique source for the identification of further genes underlying this disorder.

Epigenetically deregulated microRNA-375 is involved in a positive feedback loop with estrogen receptor alpha in breast cancer cells

Estrogen receptor α (ERα) upregulation causes abnormal cell proliferation in about two thirds of breast cancers, yet understanding of the underlying mechanisms remains incomplete. Here, we show that high expression of the microRNA miR-375 in ERα-positive breast cell lines is a key driver of their proliferation. miR-375 overexpression was caused by loss of epigenetic marks including H3K9me2 and local DNA hypomethylation, dissociation of the transcriptional repressor CTCF from the miR-375 promoter, and interactions of ERα with regulatory regions of miR-375. Inhibiting miR-375 in ERα-positive MCF-7 cells resulted in reduced ERα activation and cell proliferation. A combination of expression profiling from tumor samples and miRNA target prediction identified RASD1 as a potential miR-375 target. Mechanistic investigations revealed that miR-375 regulates RASD1 by targeting the 3' untranslated region in RASD1 mRNA. Additionally, we found that RASD1 negatively regulates ERα expression. Our findings define a forward feedback pathway in control of ERα expression, highlighting new strategies to treat ERα-positive invasive breast tumors.

Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3

As part of a large-scale, systematic effort to unravel the molecular causes of autosomal recessive mental retardation, we have previously described a novel syndrome consisting of mental retardation, coloboma, cataract and kyphosis (Kahrizi syndrome, OMIM 612713) and mapped the underlying gene to a 10.4-Mb interval near the centromere on chromosome 4. By combining array-based exon enrichment and next generation sequencing, we have now identified a homozygous frameshift mutation (c.203dupC; p.Phe69LeufsX2) in the gene for steroid 5α-reductase type 3 (SRD5A3) as the disease-causing change in this interval. Recent evidence indicates that this enzyme is required for the conversion of polyprenol to dolichol, a step that is essential for N-linked protein glycosylation. Independently, another group has recently observed SRD5A3 mutations in several families with a type 1 congenital disorder of glycosylation (CDG type Ix, OMIM 212067), mental retardation, cerebellar ataxia and eye disorders. Our results show that Kahrizi syndrome and this CDG Ix subtype are allelic disorders, and they illustrate the potential of next-generation sequencing strategies for the elucidation of single gene defects.

A report of 8 cases with hemoglobin H disease in an Iranian family

alpha-Thalassemia is a common genetic disorder in Iran. However, no comprehensive data on epidemiology of severe forms of alpha-thalassemia, including hemoglobin H (HbH) or hydrops fetalis, is available in this population. This is a first case report of an Iranian family with large number of HbH individuals. The proband is a 48-year-old woman, referred to our center with anemia and no history of previous blood transfusions. Similar clinical phenotype has been observed in all of her 5 siblings, 2 of her 4 children, and her granddaughter, whose parents are first cousins. A reverse hybridization assay covering 21 alpha globin mutations was performed to determine the genotype in 11 members of this family and a fetus. HbH genotype was identified in 9 individuals, representing 3 generations, including a fetus. The high prevalence of alpha-thalassemia carriers together with the high rate of consanguineous marriages could lead to a large number of individuals with HbH or even hydrops fetalis in Iranian families. Therefore, to avoid the risk of having affected offspring, carrier detection, genetic counseling, and prenatal diagnosis would be of vital importance for individuals with low red blood cell (RBC) indices, normal iron status, and normal HbA(2) level, who are suspected to be alpha-thalassemia carriers.

Common MEFV mutation analysis in 36 Iranian patients with familial Mediterranean fever: clinical and demographic significance

The aim of our study was to determine the spectrum of the 12 most common familial Mediterranean fever gene (MEFV) mutations in Iranian patients with heterogeneous ethnicity, using the familial Mediterranean fever (FMF) strip assay test. A total of 36 patients were diagnosed according to established clinical criteria. Genomic DNA from all patients was tested for 12 common mutations located in exon 2 (E148Q), 3 (P369S), 5 (F479L), 10 [M680I (G>C), M680I (G>A), I692del, M694V, M694I, K695R, V726A, A744S, R761H], respectively, using the FMF strip assay test. Of the 35 patients with mutations, ten were homozygote, 20 were compound heterozygote, and five were heterozygote. The most frequent genotype was M680I/M680I (6 patients, 16.7%). The most frequent mutation was M680I, followed by M694V, and V726A. The FMF strip assay test for common these 12 mutations was positive in 90.6% of alleles in this study, indicating that it appears to be an effective method for FMF mutation screening in Iranian patients.

miRNA mutations are not a common cause of deafness

Mutations in miRNA genes have been implicated in hearing loss in human families and mice. It is also possible that mutations in miRNA binding sites of inner ear targets alter gene expression levels and lead to hearing loss. To investigate these possibilities we screened predicted target genes of the miR-183 miRNA cluster known to be expressed in the inner ear sensory epithelium. In one Iranian family segregating autosomal recessive non-syndromic hearing loss (ARNSHL), we identified a homozygous variant in a predicted miR-96/182 binding site in the 3'UTR of the RDX (DFNB24) gene. However, in vitro functional studies showed that this site is not a functional target for miR-96/182. We extended our study to include the miR-183 genes themselves and 24 additional predicted target genes of the miRNA-183 cluster. Screening these miRNAs and target sequences in numerous families segregating either autosomal dominant non-syndromic deafness (ADNSHL) or ARNSHL did not identify any potential deafness-causing mutations. These results suggest that mutations disrupting gene regulation by the miR-183 cluster are not a common cause of human hearing loss.

Novel mutations in the calreticulin gene core promoter and coding sequence in schizoaffective disorder

We have recently reported the first case of mutation in the core promoter sequence of the human calreticulin gene in a family case of schizoaffective disorder. Remarkably, this gene coincides with a region of suggested linkage at 19p13.2, identified in a whole genome scan [Hamshere et al. (2005); Arch Gen Psychiatry 62;1081-1088]. The identified mutation was located at the conserved position -48 from the transcription start site, and was shown to be of functional effect, resulting in the aberrant expression of the gene. Following screening of the gene in 60 independent cases of schizoaffective disorder, we report novel germ-line mutations at positions -205 C > T and the conserved exon 5 (c: 682 C > T, pro228ser) in two unrelated cases of schizoaffective disorder. These mutations were disease-specific, and as for the -48 G > C mutation, neither was detected in a control population of 370 individuals, indicating a contribution of 3.17% in this sample series. To our knowledge, this is the first instance of disease-specific mutations in schizoaffective disorder, which warrants systematic screening of the regulatory and coding regions of the calreticulin gene in this disorder.

Variable hearing impairment in a DFNB2 family with a novel MYO7A missense mutation

Myosin VIIA mutations have been associated with non-syndromic hearing loss (DFNB2; DFNA11) and Usher syndrome type 1B (USH1B). We report clinical and genetic analyses of a consanguineous Iranian family segregating autosomal recessive non-syndromic hearing loss (ARNSHL). The hearing impairment was mapped to the DFNB2 locus using Affymetrix 50K GeneChips; direct sequencing of the MYO7A gene was completed. The Iranian family (L-1419) was shown to segregate a novel homozygous missense mutation (c.1184G>A) that results in a p.R395H amino acid substitution in the motor domain of the myosin VIIA protein. As one affected family member had significantly less severe hearing loss, we used a candidate approach to search for a genetic modifier. This novel MYO7A mutation is the first reported to cause DFNB2 in the Iranian population and this DFNB2 family is the first to be associated with a potential modifier. The absence of vestibular and retinal defects, and less severe low frequency hearing loss, is consistent with the phenotype of a recently reported Pakistani DFNB2 family. Thus, we conclude this family has non-syndromic hearing loss (DFNB2) rather than USH1B, providing further evidence that these two diseases represent discrete disorders.

Novel extreme homozygote haplotypes at the human caveolin 1 gene upstream purine complex in sporadic Alzheimer's disease

Aberrant expression of the caveolin-1 (CAV1) gene is associated with Alzheimer's disease (AD) brain. We have recently reported a polymorphic purine stretch located at between 1.8 and 1.5 kb flanking the CAV1 gene, whose alleles and genotypes are associated with late-onset AD. Extra-short homozygote haplotypes were observed that were present only in the AD cases. Following an independent case/control study, we report alleles at the other extreme of the allele range, haplotypes of which were observed to be homozygous across the region in the AD cases. We propose that there is a window for the length of motifs and haplotypes in the controls. Homozygosity for shorter and longer motifs and haplotypes was linked with AD in our study. Our findings elucidate novel predisposing haplotypes at the CAV1 gene purine complex, and confirm the role of this region in the etiopathophysiology of late-onset AD.

Identification of mutations in TRAPPC9, which encodes the NIK- and IKK-beta-binding protein, in nonsyndromic autosomal-recessive mental retardation

Mental retardation/intellectual disability is a devastating neurodevelopmental disorder with serious impact on affected individuals and their families, as well as on health and social services. It occurs with a prevalence of approximately 2%, is an etiologically heterogeneous condition, and is frequently the result of genetic aberrations. Autosomal-recessive forms of nonsyndromic MR (NS-ARMR) are believed to be common, yet only five genes have been identified. We have used homozygosity mapping to search for the gene responsible for NS-ARMR in a large Pakistani pedigree. Using Affymetrix 5.0 single nucleotide polymorphism (SNP) microarrays, we identified a 3.2 Mb region on 8q24 with a continuous run of 606 homozygous SNPs shared among all affected members of the family. Additional genotype data from microsatellite markers verified this, allowing us to calculate a two-point LOD score of 5.18. Within this region, we identified a truncating homozygous mutation, R475X, in exon 7 of the gene TRAPPC9. In a second large NS-ARMR/ID family, previously linked to 8q24 in a study of Iranian families, we identified a 4 bp deletion within exon 14 of TRAPPC9, also segregating with the phenotype and truncating the protein. This gene encodes NIK- and IKK-beta-binding protein (NIBP), which is involved in the NF-kappaB signaling pathway and directly interacts with IKK-beta and MAP3K14. Brain magnetic resonance imaging of affected individuals indicates the presence of mild cerebral white matter hypoplasia. Microcephaly is present in some but not all affected individuals. Thus, to our knowledge, this is the sixth gene for NS-ARMR to be discovered.

Skew in the human caveolin 1 gene upstream purine complex homozygote haplotype compartment in multiple sclerosis

Caveolin 1 (CAV1) is a component of the myelin sheath and the expression of the gene encoding this protein is increased during myelination in Schwann cells and oligodendrocytes. We sought to investigate the homozygote haplotype compartment in a recently identified polymorphic purine complex at the upstream region of the human CAV1 gene in multiple sclerosis (MS). In a case/control study design, the region was characterized in 126 cases of MS diagnosed based on the Revised McDonald diagnostic criteria, and 460 controls. We report a skew in the homozygote haplotype compartment in the cases versus controls both in a qualitative and quantitative respect. Excess homozygosity for haplotypes was observed in the MS cases (corrected p<0.012, OR=2.54, CI 1.14-5.64). Furthermore, we observed eight homozygote haplotypes in the MS cases that were non-existent in the controls (p<0.0003, OR=20.27, CI 2.50-163.8). For the first time, our data highlight the CAV1 upstream purine complex as a novel susceptibility genomic locus in the pathophysiology of MS. Of utmost importance, the region has been conserved across species, including mouse, guinea pig, rhesus macaque, and human. The functional effect of this region remains to be clarified in the future studies.

Mutations in LOXHD1, an evolutionarily conserved stereociliary protein, disrupt hair cell function in mice and cause progressive hearing loss in humans

Hearing loss is the most common form of sensory impairment in humans and is frequently progressive in nature. Here we link a previously uncharacterized gene to hearing impairment in mice and humans. We show that hearing loss in the ethylnitrosourea (ENU)-induced samba mouse line is caused by a mutation in Loxhd1. LOXHD1 consists entirely of PLAT (polycystin/lipoxygenase/alpha-toxin) domains and is expressed along the membrane of mature hair cell stereocilia. Stereociliary development is unaffected in samba mice, but hair cell function is perturbed and hair cells eventually degenerate. Based on the studies in mice, we screened DNA from human families segregating deafness and identified a mutation in LOXHD1, which causes DFNB77, a progressive form of autosomal-recessive nonsyndromic hearing loss (ARNSHL). LOXHD1, MYO3a, and PJVK are the only human genes to date linked to progressive ARNSHL. These three genes are required for hair cell function, suggesting that age-dependent hair cell failure is a common mechanism for progressive ARNSHL.

Hb Dhonburi (Neapolis) [β126(H4)Val→Gly] Identified in a Family from Northern Iran

Thalassemias are the most common hereditary diseases in Iran, resulting from synthesis defects in one or more hemoglobin (Hb) subunits. The majority of patients suffer from beta-thalassemia (thal), but cases with microcytic hypochromic anemia and normal electrophoretic patterns are suspected to have alpha- or silent beta-thal. A family from the northern part of Iran, an area highly prevalent for thalassemias, was referred to us for prenatal diagnosis. The hematological data of the father indicated a pattern of beta-thal minor. Reverse hybridization analysis for the most common beta-globin mutations identified IVS-II-1 (G-->A) in the heterozygous state. The maternal laboratory data indicated a case more compatible with alpha-thal. Iron deficient anemia was ruled out, and common alpha-thal point mutations and deletions were investigated. As no mutation was detected, chain synthesis was performed and showed an alpha/beta chain ratio of 2.1, that was in the range of beta-thal minor. DNA sequencing of the entire beta-globin gene identified a heterozygous GTG-->GGG (Val-->Gly) mutation at codon 126, also known as Hb Dhonburi (Neapolis). Prenatal diagnosis of the fetal DNA showed the absence of the IVS-II-1 and codon 126 anomalies. This result demonstrates the importance of screening of individuals with mild microcytic hypochromic anemia for both alpha- and silent beta-thal mutations.

Globin Chain Synthesis is a Useful Complementary Tool in the Differential Diagnosis of Thalassemias

The present study aimed at differentiating rare types of heterozygous beta-thalassemia (thal) with normal Hb A(2) values from alpha-thal in Iranian carriers by globin chain synthesis in addition to other hematological parameters. Our study groups consisted of 51 normal subjects, 24 heterozygous beta- thalassemic subjects with high Hb A(2), 62 alpha-thal-2 subjects, 34 alpha-thal-1 subjects, six Hb H disease thalassemic subjects, 14 silent beta-thal subjects with normal Hb A(2) values, five deltabeta-thal subjects and two subjects with an association of alpha- and deltabeta-thal (total = 198). Analysis of globin chains was performed by high performance liquid chromatography (HPLC). The results showed that the alpha/beta ratio averages were close to the ones in the published literature, but with a greater standard deviation and a wider range. Globin chain synthesis (GCS) could be valuable in differentiating between microcytosis produced by silent beta-thal (heterozygous beta-thal with a normal Hb A(2) level) and that caused by alpha-thal. Since the complex genotype/phenotype relationship can lead to diagnostic difficulties, GCS cannot be used as the only diagnostic tool for thalassemia carrier detection. Therefore, a combination of different tests for each patient is required.

Identification of SLC26A4 gene mutations in Iranian families with hereditary hearing impairment

Mutations in the SLC26A4 gene at the DFNB4 locus are responsible for Pendred syndrome and non-syndromic hereditary hearing loss (DFNB4). This study included 80 nuclear families with two or more siblings segregating presumed autosomal recessive hearing loss. All deaf persons tested negative for mutations in GJB2 at the DFNB1 locus and were, therefore, screened for autozygosity by descent (ABD) using short tandem repeat polymorphisms (STRPs) that flanked SLC26A4. In 12 families, homozygosity for STRPs suggested possible ABD in this genomic region. Affected individuals in five families had a positive perchlorate discharge test. Sequence analysis of SLC26A4 identified ten mutations in eight families (T420I, 1197delT, G334V, R409H, T721M, R79X, S448L, L597S, 965insA and L445W), of which, four are novel (T420I, G334V, 965insA and R79X). These results imply that Pendred syndrome is the most prevalent form of syndromic hereditary hearing loss in Iran.

A large deletion in GPR98 causes type IIC Usher syndrome in male and female members of an Iranian family

BACKGROUND

Usher syndrome (USH) is a clinically and genetically heterogeneous disease. The three recognised clinical phenotypes (types I, II and III; USH1, USH2 and USH3) are caused by mutations in nine different genes. USH2C is characterised by moderate to severe hearing loss, retinitis pigmentosa and normal vestibular function. One earlier report describes mutations in GPR98 (VLGR1) in four families segregating this phenotype.

OBJECTIVE

To detect the disease-causing mutation in an Iranian family segregating USH2C. In this family, five members had a phenotype compatible with Usher syndrome, and two others had nonsyndromic hearing loss.

METHODS

Mutation analysis of all 90 coding exons of GPR98.

RESULTS

Consistent with these clinical findings, the five subjects with USH carried a haplotype linked to the USH2C locus, whereas the two subjects with nonsyndromic hearing loss did not. We identified a new mutation in GPR98 segregating with USH2C in this family. The mutation is a large deletion g.371657_507673del of exons 84 and 85, presumably leading to a frameshift.

CONCLUSIONS

A large GPR98 deletion of 136 017 bp segregates with USH2C in an Iranian family. To our knowledge, this is only the second report of a GPR98 mutation, and the first report on male subjects with USH2C and a GPR98 mutation.