Identification of a novel mutation in DKC1 in dyskeratosis congenita.

Dyskeratosis congenita (DC) is a rare congenital syndrome characterized by the triad of reticular skin pigmentation, nail dystrophy and mucosal leukoplakia, and the predisposition to bone marrow failure and malignancy. DC is genetically heterogeneous and X-linked and autosomal forms of the disease exist. Here, we report the clinical description and mutation analysis of a Russian family with X-linked DC. A novel mutation in DKC1 raised de novo in the maternal grandmother's gamete was found; this mutation is a 2 bp inversion in exon 3: NM_001363:c.166_167invCT (Leu56Ser).

Mutant small heat-shock protein 27 causes axonal Charcot-Marie-Tooth disease and distal hereditary motor neuropathy.

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuromuscular disease and is characterized by considerable clinical and genetic heterogeneity. We previously reported a Russian family with autosomal dominant axonal CMT and assigned the locus underlying the disease (CMT2F; OMIM 606595) to chromosome 7q11-q21 (ref. 2). Here we report a missense mutation in the gene encoding 27-kDa small heat-shock protein B1 (HSPB1, also called HSP27) that segregates in the family with CMT2F. Screening for mutations in HSPB1 in 301 individuals with CMT and 115 individuals with distal hereditary motor neuropathies (distal HMNs) confirmed the previously observed mutation and identified four additional missense mutations. We observed the additional HSPB1 mutations in four families with distal HMN and in one individual with CMT neuropathy. Four mutations are located in the Hsp20-alpha-crystallin domain, and one mutation is in the C-terminal part of the HSP27 protein. Neuronal cells transfected with mutated HSPB1 were less viable than cells expressing the wild-type protein. Cotransfection of neurofilament light chain (NEFL) and mutant HSPB1 resulted in altered neurofilament assembly in cells devoid of cytoplasmic intermediate filaments.