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Bardet-Biedl syndrome ( BBS) is an autosomal recessive multisystemic human genetic disorder characterized by six major defects including obesity, mental retardation, renal anomalies, polydactyly, retinal degeneration and hypogenitalism. In several cases of BBS, few other features such as metabolic defects, cardiovascular anomalies, speech deficits, hearing loss, hypertension, hepatic defects and high incidence of diabetes mellitus have been reported as well. The BBS displays extensive genetic heterogeneity. To date, 19 genes have been mapped on different chromosomes causing BBS phenotypes having varied mutational load of each BBS gene. In this review, we have discussed clinical spectrum and genetics of BBS. This report presents a concise overview of the current knowledge on clinical data and its molecular genetics progress upto date. [ABSTRACT FROM AUTHOR]

Although there has been significant research surrounding incidental findings (IFs), the guidelines and information provided to investigators remain unspecific, unclear, and often generalize the course of action to everyone in the field. We explored the perceptions and experiences of investigators regarding the return of IFs in genetic research. Researchers and clinician-researchers were invited to participate in semi-structured telephone interviews in Quebec and Ontario. Twenty professionals participated, and thematic analysis was used to analyze the transcriptions. Four contextual elements emerged: (i) degree of significance of results, (ii) respect for persons, (iii) infrastructure implications, and (iv) professional responsibilities. Our findings demonstrate that all investigators raised similar contextual elements surrounding the return of IFs. However, some nuances in participants' experiences of the understanding of professional responsibilities also emerged. Because of the existing nuances, a one-size-fits-all approach is inappropriate, suggesting that context ought to be considered in decisions about IFs. [ABSTRACT FROM AUTHOR]

Hereditary hair loss in human is a group of clinically and genetically heterogeneous disorders. It is characterized by sparse to complete absence of hair on the scalp and other parts of the body. In few cases tightly curled twisted wooly hair (WH) on the scalp has been reported as well. The hair loss disorders, including both syndromic and non-syndromic (isolated) forms, segregate either in autosomal dominant or autosomal recessive pattern. To date, seven autosomal dominant and equal numbers of autosomal recessive isolated forms of hair loss disorders have been characterized. Genes responsible for causing most of these disorders have been identified. In this review, we have provided an update on clinical and genetic aspects of isolated hereditary hair loss disorders manifesting with hypotrichosis and/or WHs. Because most of the recessive genes have been mapped using consanguineous families of Pakistani origin, therefore emphasis is given to mutations identified in these families. OMIM nomenclature has been followed to indicate different forms of hair loss disorders. [ABSTRACT FROM AUTHOR]

Lee K, Khan S, Islam A, Ansar M, Andrade PB, Kim S, Santos-Cortez RLP, Ahmad W, Leal SM. Novel TMPRSS3 variants in Pakistani families with autosomal recessive non-syndromic hearing impairment. Mutations in the TMPRSS3 gene are known to cause autosomal recessive non-syndromic hearing impairment (ARNSHI). After undergoing a genome scan, 10 consanguineous Pakistani families with ARNSHI were found to have significant or suggestive evidence of linkage to the TMPRSS3 region. In order to elucidate if the TMPRSS3 gene is responsible for ARNSHI in these families, the gene was sequenced using DNA samples from these families. Six TMPRSS3 variants were found to cosegregate in 10 families. None of these variants were detected in 500 control chromosomes. Four novel variants, three of which are missense [c.310G>A (p.Glu104Lys), c.767C>T (p.Ala256Val) and c.1273T>C (p.Cys425Arg)] and one nonsense [c.310G>T (p.Glu104Stop)], were identified. The pathogenicity of novel missense variants was investigated through bioinformatics analyses. Additionally, the previously reported deletion c.208delC (p.His70ThrfsX19) was identified in one family and the known mutation c.1219T>C (p.Cys407Arg) was found in five families, which makes c.1219T>C (p.Cys407Arg) as the most common TMPRSS3 mutation within the Pakistani population. Identification of these novel variants lends support to the importance of elements within the low-density lipoprotein receptor A (LDLRA) and serine protease domains in structural stability, ligand binding and proteolytic activity for proper TMPRSS3 function within the inner ear. [ABSTRACT FROM AUTHOR]

Khan S, Basit S, Zimri FK, Ali N, Ali G, Ansar M, Ahmad W. A novel homozygous missense mutation in WNT10B in familial split-hand/foot malformation. Split-hand/foot malformation (SHFM) is a rare limb developmental malformation, characterized by variable degree of median clefts of hands and feet due to the absence of central rays of extremities. To date, six different forms of SHFM have been described. Four of these SHFM1, SHFM3, SHFM4 and SHFM5 show autosomal dominant, SHFM6 autosomal recessive and SHFM2 X-linked pattern of inheritance. In this study a large consanguineous Pakistani family, with autosomal recessive SHFM, appeared in the last two generations, was investigated. In total 15 individuals including 9 males and 6 females were affected with the syndrome. Affected members of the family exhibited SHFM phenotype with involvement of hands and feet. Most of the affected members showed syndactyly/polydactyly in hands and feet, dysplastic hand, aplasia of radial ray of hand and cleft foot. Investigating linkage to known autosomal SHFM loci mapped the family to SHFM6 locus on chromosome 12p11.1-q13.13. Mutation screening of the gene WNT10B revealed a novel sequence variant (c.986C>G, p.Thr329Arg) in all affected individuals who were studied. This is the third mutation reported in gene WNT10B causing autosomal recessive SHFM syndrome. [ABSTRACT FROM AUTHOR]

Moslehi R, Signore C, Tamura D, Mills JL, DiGiovanna JJ, Tucker MA, Troendle J, Ueda T, Boyle J, Khan SG, Oh K-S, Goldstein AM, Kraemer KH. Adverse effects of trichothiodystrophy DNA repair and transcription gene disorder on human fetal development. The effects of DNA repair and transcription gene abnormalities in human pre-natal life have never been studied. Trichothiodystrophy (TTD) is a rare (affected frequency of 10−6) recessive disorder caused by mutations in genes involved in nucleotide excision repair (NER) pathway and in transcription. Based on our novel clinical observations, we conducted a genetic epidemiologic study to investigate gestational outcomes associated with TTD. We compared pregnancies resulting in TTD-affected offspring ( n = 24) with respect to abnormalities during their antenatal and neonatal periods to pregnancies resulting in their unaffected siblings ( n = 18), accounting for correlation, and to population reference values. Significantly higher incidence of several severe gestational complications was noted in TTD-affected pregnancies. Small for gestational age (SGA) <10th percentile [Relative risk (RR ) = 9.3, 95% CI = 1.4–60.5, p = 0.02], SGA <3rd percentile (RR = 7.2, 95% CI = 1.1–48.1, p = 0.04), and neonatal intensive care unit (NICU) hospitalization (RR = 6.4, 95% CI = 1.4–29.5, p = 0.02) occurred more frequently among TTD-affected neonates compared with their unaffected siblings. Compared with reference values from general obstetrical population, pregnancies that resulted in TTD-affected infants were significantly more likely to be complicated by hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome (RR = 35.7, 95% CI = 7.6–92.5, p = 0.0002), elevated mid-trimester maternal serum human chorionic gonadotropin (hCG) levels (RR = 14.3, 95% CI = 7.0–16.6, p < 0.0001), SGA <3rd percentile (RR = 13.9, 95% CI = 7.4–21.1, p < 0.0001), pre-term delivery (<32 weeks) (RR = 12.0, 95% CI = 4.9–21.6, p < 0.0001), pre-eclampsia (RR = 4.0, 95% CI = 1.6–7.4, p = 0.006), and decreased fetal movement (RR = 3.3, 95% CI = 1.6–5.2, p = 0.0018). Abnormal placental development is an underlying mechanism that may explain the constellation of observed complications in our study. Thus, we hypothesize that TTD DNA repair and transcription genes play an important role in normal human placental development. [ABSTRACT FROM AUTHOR]

Autosomal recessive nonsyndromic hearing impairment (ARNSHI) segregating in three unrelated, large consanguineous Pakistani families (PKDF528, PKDF859 and PKDF326) is linked to markers on chromosome 12q14.2-q15. This novel locus is designated DFNB74. Maximum two-point limit of detection (LOD) scores of 5.6, 5.7 and 2.6 were estimated for markers D12 S313, D12 S83 and D12 S75 at θ = 0 for recessive deafness segregating in these three families. Haplotype analyses identified a critical linkage interval of 5.35 cM (5.36 Mb) defined by D12 S329 at 74.58 cM and D12 S313 at 79.93 cM. DFNB74 is the second ARNSHI locus mapped to chromosome 12, but the physical intervals do not overlap with one another. A locus contributing to the early onset, rapidly progressing hearing loss of A/J mice ( ahl4, age-related hearing loss 4) was reported to map to chromosome 10 in a region of conserved synteny to DFNB74, suggesting that ahl4 and DFNB74 may be due to mutations of the same gene in these two species. [ABSTRACT FROM AUTHOR]

Usher syndrome (USH) is a hereditary disorder associated with sensorineural hearing impairment, progressive loss of vision attributable to retinitis pigmentosa (RP) and variable vestibular function. Three clinical types have been described with type I (USH1) being the most severe. To date, six USH1 loci have been reported. We ascertained two large Pakistani consanguineous families segregating profound hearing loss, vestibular dysfunction, and RP, the defining features of USH1. In these families, we excluded linkage of USH to the 11 known USH loci and subsequently performed a genome-wide linkage screen. We found a novel USH1 locus designated USH1H that mapped to chromosome 15q22-23 in a 4.92-cM interval. This locus overlaps the non-syndromic deafness locus DFNB48 raising the possibility that the two disorders may be caused by allelic mutations. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented on mutations in the OTOA gene (MIM 607038) which causes autosomal recessive nonsyndromic hearing impairment.