Dimerization is necessary for MIM-mediated membrane deformation and endocytosis.

MIM [missing in metastasis; also called MTSS1 (metastasis suppressor 1)] is an intracellular protein that binds to actin and cortactin and has an intrinsic capacity to sense and facilitate the formation of protruded membranous curvatures implicated in cellular polarization, mobilization and endocytosis. The N-terminal 250 amino acids of MIM undergo homodimerization and form a structural module with the characteristic of an I-BAR [inverse BAR (Bin/amphiphysin/Rvs)] domain. To discern the role of the dimeric configuration in the function of MIM, we designed several peptides able to interfere with MIM dimerization in a manner dependent upon their lengths. Overexpression of one of the peptides effectively abolished MIM-mediated membrane protrusions and transferrin uptake. However, a peptide with a high potency inhibiting MIM dimerization failed to affect its binding to actin and cortactin. Thus the results of the present study indicate that the dimeric configuration is essential for MIM-mediated membrane remodelling and serves as a proper target to develop antagonists specifically against an I-BAR-domain-containing protein.

[c.359T>C mutation of the MYH14 gene in two autosomal dominant non-syndromic hearing impairment families with common ancestor].

OBJECTIVE: To identify the gene mutation for two Chinese families with autosomal dominant non-syndromic hearing impairment(NSHI). METHODS: Two NSHI pedigrees with common ancestor were identified by clinical examination and family investigation. Linkage analysis was performed for all known NSHI loci, and all exons and exon-intron boundaries of the non-muscle myosin heavy chain 14 (MYH14) gene were amplified by PCR and sequenced. RESULTS: The disease-causing gene of these 2 pedigrees was fine mapped to the DFNA4 locus on 19q13.33. A heterozygous transition of c. 359T>C (p.S120L) in MYH14 gene was identified. The mutation was detected in all patients but not in normal members in the two families. CONCLUSION: It is the first report that mutation in MYH14 gene can cause dominant non-syndromic hearing impairment in Asian population, suggesting that MYH14 gene can be a disease-causing gene of Chinese patients with hearing impairment.

Repression of MHC class I transcription by HPV16E7 through interaction with a putative RXRbeta motif and NF-kappaB cytoplasmic sequestration.

Down-regulation of transcription of the MHC class I genes in HPV16 tumorigenic cells is partly due to HPV16E7 associated with the MHC class I promoter and repressed chromatin activation. In this study, we further demonstrated that HPV16E7 is physically associated with a putative RXRbeta binding motif (GGTCA) of the proximal promoter of the MHC class I genes by using reporter transcriptional assays and chromatin immunoprecipitation assays. Our data also provide evidence that HPV16E7 inhibits TNF-alpha-induced up-regulation of MHC class I transcription by impaired nuclear translocation of NF-kappaB. More importantly, CaSki tumor cells treated with TSA and transfected with the constitutively active mutant form of IKK-alpha (which can activate NF-kappaB directly) showed a maximal level of up-regulation of MHC-I expression. Taken together, our results suggest that HPV16E7 may employ two independent mechanisms to ensure that either the constitutive or inducible transcription of MHC class I genes is down-regulated.

[A novel COL4A5 splicing mutation causing Alport syndrome in a Chinese family].

OBJECTIVE: To identify the pathogenic mutation in a Chinese family with Alport syndrome. METHODS: Blood samples were collected from the members of the family. Direct DNA sequence analysis of the entire coding region and exon-intron boundaries of the COL4A5 gene was performed, and restriction fragment length polymorphism (RFLP) analysis was used to confirm the sequencing results and to test the mutation in all the family members and 200 controls. RESULTS: A novel splicing mutation of c.1517-1G to T in the COL4A5 gene was identified in all patients in the family. RFLP analysis did not detect this mutation in all the unaffected family members and the 200 controls. CONCLUSION: This data revealed a novel splicing mutation of c.1517-1G to T in the COL4A5 gene causing Alport syndrome in a Chinese family. Author's study enriched the spectrum of COL4A5 mutation associated with Alport syndrome.

Mucolipidosis in a Chinese family with compound heterozygous mutations at the GNPTAB gene.

BACKGROUND: Mucopolysaccharidoses (MPS) are caused by the deficiency in the metabolism of one or more types of mucopolysaccharides or glycosaminoglycans (GAGs). Mucolipidoses (ML) are a group of genetic disorders in which both glycosaminoglycans (GAGs) and sphingolipids build up in the body. Both of MPS and ML belong to lysosomal storage diseases and show similar clinical manifestations. Distinction of these two types of diseases has not been always possible using conventional clinical diagnoses. Genetic test provides a definitive diagnosis for ML and MPS diseases. METHODS: The initial clinical diagnosis had suspected the proband as either MPS or ML. To verify the clinical diagnosis, linkage analysis was performed with a panel of microsatellite markers flanking 10 candidate genetic loci for mucopolysaccharidosis and 2 loci for mucolipidosis. Two-point logarithm of odds (lod) scores was calculated using Linkage Package 5.2 program. Direct DNA sequence analyses of GNPTAB in the family members were performed. RESULTS: By using linkage and mutational analyses, we have identified that the family members contain compound heterozygous mutations of p.R364X and c.2715+1G>A in the GNPTAB gene. We determine the family as MLIII based on the DNA-test and clinical diagnoses. CONCLUSION: Our study confirms the pathological relationship between the patients' genotype and phenotype in the clinical ML manifestation, and suggests that DNA-based diagnosis serves as a better way to define ML and MPS.

A novel SCN1A missense mutation causes generalized epilepsy with febrile seizures plus in a Chinese family.

Generalized epilepsy with febrile seizures plus (GEFS(+)) is a common familial epilepsy syndrome, which generally develops in childhood. GEFS(+) is caused by mutations in the sodium-channel α1-subunit (SCN1A). In this report, we investigated a Chinese family with an autosomal dominant form of GEFS(+). The affected GEFS(+) patients in this family displayed significant inter-family clinical heterogeneity. Linkage analysis localized the disease-causing gene to chromosome 2q24, where SCN1A is located. Furthermore, DNA sequencing of the whole coding region of SCN1A revealed a novel heterozygous nucleotide substitution (c.577C>T) causing a missense mutation (p.L193F) in the S3 segment of SCN1A domain D1. Our results expand the spectrum of SCN1A mutations and provide novel insights between the SCN1A mutations and the clinical variations of GEFS(+).