Met-induced membrane blebbing leads to amoeboid cell motility and invasion.

Met tyrosine kinase has been implicated in tumorigenesis and metastasis; its overexpression and deregulation is often observed in cancer. Although Met's functions in cell motility has been studied extensively, its involvement in bleb-based, amoeboid motility is yet to be determined. The aim of this work is to study the role of Met in amoeboid cell motility and invasion. We show that aggressive breast cancer cells expressing high levels of endogenous Met, as well as HEK293T cells over expressing fluorescent Met, exhibit constitutive, ligand-independent Met activation, leading to Met-dependent membrane blebbing and amoeboid cell motility; HEK293T cells over expressing fluorescent Met were able to invade in three-dimensional matrix. Hyper-activated Met mutant significantly enhances blebbing and cell motility. Met inhibition by either a Met-specific inhibitor or by exogenous expression of a dominant-negative Met remarkably repressed membrane blebbing and invasion. Inhibition of Rho signaling pathway by a ROCK inhibitor also represses Met-induced blebbing, suggesting that Met regulates the blebbing machinery through Rho-ROCK pathway, which controls the actin-myosin contractile force. Either de-polymerization or hyper-polymerization of the actin cytoskeleton abrogates Met-induced blebbing, signifying that actin polymerization has a role in halting and retracting Met-induced mature blebs. Indeed, when blebs retract, membrane wrinkles containing high levels of Met and actin are generated, indicating localized formation of Met-signaling microdomains. We suggest that this bleb-based activity is induced by amplification of Met signaling in unique membrane domains generated by bleb retraction. Our results indicate that Met-induced blebbing has an important role in cell detachment, amoeboid motility and invasion ability, which are utilized by cancer cells for migration and metastasis.

A novel splice-site mutation in the AAGAB gene segregates with hereditary punctate palmoplantar keratoderma and congenital dysplasia of the hip in a large family.

BACKGROUND: Palmoplantar keratoderma punctata (PPKP) is a heterogeneous group of disorders characterized by hyperkeratotic papules occurring over the palms and soles during adolescence. PPKP type 1, also known as PPKP Buschke-Fischer-Brauer type, was recently found to result from mutations in the AAGAB gene, encoding the p34 protein. PPKP type 1 is usually not associated with extracutaneous features. AIM: To investigate a large family in which PPKP1 was present in association with congenital dysplasia of the hip (CDH). METHODS: A combination of direct sequencing of candidate genes and reverse-transcription PCR was used to identify the molecular basis underlying the clinical features displayed by the patients. RESULTS: Direct sequencing showed a novel intronic mutation in AAGAB, which was found to cosegregate with PPKP and CDH throughout the family. The mutation was found to result in aberrant RNA splicing, leading to exon 4 skipping. CONCLUSIONS: This observation suggests either the existence of a CDH-associated gene in the vicinity of AAGAB, or a hitherto unrecognized role for p34 during skeletal development.

Non-syndromic autosomal recessive congenital ichthyosis in the Israeli population.

BACKGROUND: Autosomal recessive congenital ichthyosis (ARCI) is the term given to a complex and heterogeneous group of cornification disorders associated with mutations in at least eight distinct genes. Mutation distribution and prevalence rates are instrumental for the design of diagnostic strategies in ARCI but have not yet been systematically explored in the Israeli population. Previous data suggest that the demographic features specific to Middle Eastern populations, such as a high frequency of consanguineous marriages, may have an effect on the molecular epidemiology of genodermatoses. METHODS: We systematically assessed all families with ARCI presenting at our clinics over a period of 9 years, using a combination of homozygosity mapping, direct sequencing and PCR-restriction fragment length polymorphism assays. RESULTS: In total, 20 families with ARCI were assessed, and causative mutations were identified in 7 genes: TGM1 (30% of patients), ALOX12B (20%), ABCA12 (5%), CYP4F22 (10%), ALOXE3 (10%), LIPN (5%) and NIPAL4 (5%) Two families (10%) had mutations mapped to an ARCI-associated locus on 12p11.2-q13, while no mutation was found for one additional kindred. In the subgroup of families of Arab Muslim origin, mutations were identified most frequently in ALOX12B and TGM1 (31%), whereas the other subgroups displayed a subtype distribution very similar to that previously reported in western populations. CONCLUSIONS: The present data point to the need for population-tailored mutation screening strategies in genetically heterogeneous genodermatoses, based on the relative prevalence of the disease subsets.

Beneficial effect of acitretin in Chanarin-Dorfman syndrome.

Chanarin-Dorfman syndrome (CDS) is an autosomal recessive metabolic disorder characterized by congenital ichthyosis and visceral complications due to accumulation of neutral lipids. CDS is caused by mutations in the ABHD5 (previously termed CGI-58) gene. In the present study, we assessed a young child presenting with ichthyosis and hepatomegaly, suggesting a diagnosis of CDS. We identified an intronic mutation, c.960 + 5G>A, which was found to result in skipping of exon 6. Abnormal results on liver function tests led us to treat the child with acitretin, which resulted in satisfactory clinical and laboratory responses. The present case illustrates the beneficial effect of acitretin treatment in CDS even in the presence of compromised liver function.