A Recurrent Intragenic Deletion in the Desmoglein 4 Gene Underlies Localized Autosomal Recessive Hypotrichosis

6 páginas, 2 figuras.A newly defined form of inherited hair loss, named localized autosomal recessive hypotrichosis (LAH, OMIM 607903), was recently described in the literature (Kljuic et al. 2003a; Rafique et al. 2003) and shown to be linked to chromosome 18. We identified a large, intragenic deletion in the desmoglein 4 gene (DSG4) as the underlying mutation in two unrelated families of Pakistani origin (Kljuic et al. 2003a). LAH is an autosomal recessive form of hypotrichosis affecting the scalp, trunk, and extremities, and largely sparing the facial, pubic, and axillary hair. Typical hairs are fragile and break easily, leaving short sparse scalp hairs with a characteristic appearance. Using comparative genomics, we also demonstrated that human LAH is allelic with the lanceolate hair (lah) mouse (Kljuic et al. 2003a), as well as the lanceolate hair (lah) rat phenotype (Jahoda et al. 2004). In order to expand the series of allelic mutations in the desmoglein 4 gene underlying LAH in humans, we begin molecular analysis of DSG4 in families from around the world. Here, we describe the study of a family of Pakistani origin with two siblings affected with LAH (Figure 1).This study was supported in part by grants USPHS NIH R01-AR44924 and the March of Dimes Birth Defects Foundation (A. M. C.).Peer reviewe

Mutations in the Cholesterol Transporter Gene ABCA5 Are Associated with Excessive Hair Overgrowth

Inherited hypertrichoses are rare syndromes characterized by excessive hair growth that does not result from androgen stimulation, and are often associated with additional congenital abnormalities. In this study, we investigated the genetic defect in a case of autosomal recessive congenital generalized hypertrichosis terminalis (CGHT) (OMIM135400) using whole-exome sequencing. We identified a single base pair substitution in the 5′ donor splice site of intron 32 in the ABC lipid transporter gene ABCA5 that leads to aberrant splicing of the transcript and a decrease in protein levels throughout patient hair follicles. The homozygous recessive disruption of ABCA5 leads to reduced lysosome function, which results in an accumulation of autophagosomes, autophagosomal cargos as well as increased endolysosomal cholesterol in CGHT keratinocytes. In an unrelated sporadic case of CGHT, we identified a 1.3 Mb cryptic deletion of chr17q24.2-q24.3 encompassing ABCA5 and found that ABCA5 levels are dramatically reduced throughout patient hair follicles. Collectively, our findings support ABCA5 as a gene underlying the CGHT phenotype and suggest a novel, previously unrecognized role for this gene in regulating hair growth

ApoB siRNA-induced Liver Steatosis is Resistant to Clearance by the Loss of Fatty Acid Transport Protein 5 (Fatp5)

The association between hypercholesterolemia and elevated serum apolipoprotein B (APOB) has generated interest in APOB as a therapeutic target for patients at risk of developing cardiovascular disease. In the clinic, mipomersen, an antisense oligonucleotide (ASO) APOB inhibitor, was associated with a trend toward increased hepatic triglycerides, and liver steatosis remains a concern. We found that siRNA-mediated knockdown of ApoB led to elevated hepatic triglycerides and liver steatosis in mice engineered to exhibit a human-like lipid profile. Many genes required for fatty acid synthesis were reduced, suggesting that the observed elevation in hepatic triglycerides is maintained by the cell through fatty acid uptake as opposed to fatty acid synthesis. Fatty acid transport protein 5 (Fatp5/Slc27a5) is required for long chain fatty acid (LCFA) uptake and bile acid reconjugation by the liver. Fatp5 knockout mice exhibited lower levels of hepatic triglycerides due to decreased fatty acid uptake, and shRNA-mediated knockdown of Fatp5 protected mice from diet-induced liver steatosis. Here, we evaluated if siRNA-mediated knockdown of Fatp5 was sufficient to alleviate ApoB knockdown-induced steatosis. We determined that, although Fatp5 siRNA treatment was sufficient to increase the proportion of unconjugated bile acids 100-fold, consistent with FATP5's role in bile acid reconjugation, Fatp5 knockdown failed to influence the degree, zonal distribution, or composition of the hepatic triglycerides that accumulated following ApoB siRNA treatment

A Recurrent Intragenic Deletion in the Desmoglein 4 Gene Underlies Localized Autosomal Recessive Hypotrichosis

6 páginas, 2 figuras.A newly defined form of inherited hair loss, named localized autosomal recessive hypotrichosis (LAH, OMIM 607903), was recently described in the literature (Kljuic et al. 2003a; Rafique et al. 2003) and shown to be linked to chromosome 18. We identified a large, intragenic deletion in the desmoglein 4 gene (DSG4) as the underlying mutation in two unrelated families of Pakistani origin (Kljuic et al. 2003a). LAH is an autosomal recessive form of hypotrichosis affecting the scalp, trunk, and extremities, and largely sparing the facial, pubic, and axillary hair. Typical hairs are fragile and break easily, leaving short sparse scalp hairs with a characteristic appearance. Using comparative genomics, we also demonstrated that human LAH is allelic with the lanceolate hair (lah) mouse (Kljuic et al. 2003a), as well as the lanceolate hair (lah) rat phenotype (Jahoda et al. 2004). In order to expand the series of allelic mutations in the desmoglein 4 gene underlying LAH in humans, we begin molecular analysis of DSG4 in families from around the world. Here, we describe the study of a family of Pakistani origin with two siblings affected with LAH (Figure 1).This study was supported in part by grants USPHS NIH R01-AR44924 and the March of Dimes Birth Defects Foundation (A. M. C.).Peer reviewe

Congenital universal hypertrichosis with deafness and dental anomalies inherited as an X-linked trait

5 páginas, 1 figura, 1 tabla.We report a large Mexican kindred with a variant form of congenital universal hypertrichosis that is inherited in an apparent X-linked recessive manner. In addition to the generalized hypertrichosis, the affected individuals have dental malformations and deafness. Males are more severely affected than females who exhibit only mild hypertrichosis, but not deafness or dental anomalies. Haplotype analysis in this pedigree revealed linkage to a 13-cM region on chromosome Xq24-q27.1 between markers GATA198A10 and DXS8106. Localization of the gene underlying this form of hypertrichosis is the initial step in identifying genes on the X chromosome that are involved in the control of hair growth and development.This work was supported in part by the Skin Disease Research Center in the Department of Dermatology at Columbia University (NIH P30 AR44535) and the Dermatology Foundation.Peer reviewe

Alterations in the hepatic transcriptional landscape after RNAi mediated ApoB silencing in cynomolgus monkeys

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Identification of mutations in the COL7A1 gene in a proband with mild recessive dystrophic epidermolysis bullosa and aortic insufficiency

12 páginas, 2 figuras.We report the clinical and molecular findings in a patient with a mild form of recessive dystrophic epidermolysis bullosa and aortic insufficiency. To our knowledge, this is the first report of association between dystrophic epidermolysis bullosa and abnormalities of the aortic valve. Analysis of the COL7A1 gene has revealed two new mutations, a 20-bp duplication and a splice site mutation.This study was supported by NIH NIAMS R01 AR43602 (A.M.C.).Peer reviewe

Silencing Myostatin Using Cholesterol-conjugated siRNAs Induces Muscle Growth

Short interfering RNAs (siRNAs) are a valuable tool for gene silencing with applications in both target validation and therapeutics. Many advances have recently been made to improve potency and specificity, and reduce toxicity and immunostimulation. However, siRNA delivery to a variety of tissues remains an obstacle for this technology. To date, siRNA delivery to muscle has only been achieved by local administration or by methods with limited potential use in the clinic. We report systemic delivery of a highly chemically modified cholesterol-conjugated siRNA targeting muscle-specific gene myostatin (Mstn) to a full range of muscles in mice. Following a single intravenous injection, we observe 85–95% knockdown of Mstn mRNA in skeletal muscle and >65% reduction in circulating Mstn protein sustained for >21 days. This level of Mstn knockdown is also accompanied by a functional effect on skeletal muscle, with animals showing an increase in muscle mass, size, and strength. The cholesterol-conjugated siRNA platform described here could have major implications for treatment of a variety of muscle disorders, including muscular atrophic diseases, muscular dystrophy, and type II diabetes