Investigation of c9orf72 in 4 neurodegenerative disorders.

OBJECTIVE To estimate the allele frequency of C9orf72 (G4C2) repeats in amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), Alzheimer disease (AD), and Parkinson disease (PD). DESIGN The number of repeats was estimated by a 2-step genotyping strategy. For expansion carriers, we sequenced the repeat flanking regions and obtained APOE genotypes and MAPT H1/H2 haplotypes.

Dual functions for connexins: Cx43 regulates growth independently of gap junction formation.

Connexins, the family of proteins that form vertebrate gap junctions, have key roles during development and in the adult. Previously, the physiological actions of connexins have been ascribed solely to formation of gap junction channels and thought to be mediated by the transfer of small molecules between neighboring cells. In conflict with this hypothesis here we demonstrate that Cx43 can affect cell growth independently of gap junction formation.

A connexin 43 mutant lacking the carboxyl cytoplasmic domain inhibits both growth and motility of mouse 3T3 fibroblasts.

Connexins have been shown to inhibit the growth of a wide number of communication-deficient cells both in vivo and in vitro, but the molecular mechanism remains largely unknown. In previous work we have shown that stable transfectants of 3T3 A31 fibroblasts, which express a Connexin 43 (Cx43) mutant (Cx43-256M) consisting of amino acids 1-256 of rat Cx43 fused to a c-myc tag, exhibit a decreased basal growth rate and weakened mitogenic response to platelet derived growth factor compared with either the parent cell line or cells transfected with an expression vector that did not encode a functional protein. Here we have investigated further the growth characteristics of these cells in order to establish the mechanism by which this protein suppresses cell growth.

Expression of a Cx43 deletion mutant in 3T3 A31 fibroblasts prevents PDGF-induced inhibition of cell communication and suppresses cell growth.

Communication through gap junctions was first suggested to have a role in the social control of cell growth over 30 years ago. However, despite extensive experimentation, the importance of gap junctions as a general mechanism of growth control remains to be established. A number of different studies have shown that a common early response of cells in culture to polypeptide growth factors such as PDGF is a rapid and transient inhibition of cell communication suggesting that a cell may have to lose communication with its neighbors before it can undergo cell division.

DNA synthesis by ovine mammary alveolar epithelial cells: effects of heparin, epidermal growth factor-related peptides and interaction with stage of pregnancy.

Amphiregulin is a heparin-binding member of the epidermal growth factor (EGF) family, which we have recently shown to be expressed in sheep mammary gland. Uniquely among known EGF-like growth factors, its mitogenic activity is inhibited by soluble heparin, but heparin-like molecules on the cell surface and/or in extracellular matrix appear to be necessary for amphiregulin to exert its biological effect. In primary cultures of sheep mammary alveolar epithelial cells, heparin (1-20 mg/l) inhibited DNA synthesis in a dose-dependent manner.