Improved culture methods to expand Schwann cells with altered growth behaviour from CMT1A patients.

A duplication of the gene for myelin protein PMP22 is by far the most common cause of the hereditary demyelinating neuropathy CMT1A. A role for PMP22 in cell growth in addition to its function as a myelin protein has been suggested because PMP22 is homologous to a gene specifically upregulated during growth arrest. Furthermore, transfected rat Schwann cells overexpressing PMP22 show reduced growth. In addition, abnormal Schwann cell differentiation has been described in nerve biopsies from CMT1A patients. To analyse whether the duplication of the PMP22 gene in CMT1A neuropathy primarily alters Schwann cell differentiation and to exclude nonspecific secondary responses, we improved human Schwann cell culturing. This allowed us long-term passaging of human Schwann cells with unchanged phenotype, assessed by expression of different Schwann cell markers. Subsequently we established Schwann cell cultures from CMT1A nerve biopsies. We find decreased proliferation of Schwann cells from different CMT1A patients in all passages. We also demonstrate PMP22 mRNA overexpression in cultured CMT1A Schwann cells. We conclude that decreased proliferation in cultured Schwann cells that carry the CMT1A duplication indicates abnormal differentiation of CMT1A Schwann cells. The identification of an abnormal phenotype of CMT1A Schwann cells in culture could possibly lead to an in vitro disease model.

Mutation analysis of a putative sialyltransferase gene, the SFRS2 splicing factor gene and the c-myb ET-locus in two families with hereditary neuralgic amyotrophy (HNA).

HNA is an autosomal dominant recurrent focal neuropathy involving the brachial plexus. The etiology of HNA is unknown but the genetic defect most likely affects a non-neuronal tissue. We previously described linkage to chromosome 17q24-q25 in two HNA-families. Here we report the mutation analysis of two candidate genes: a cDNA encoding a putative sialyltransferase and the SFRS2 splicing factor including the c-myb ET-locus which is encoded on the opposite strand of the SFRS2 gene. The complete protein coding regions of both genes were studied by direct DNA sequencing. We did not find a disease associated mutation indicating that these genes are most likely not involved in the pathogenesis of HNA. However, we identified and characterized a rare AvaII polymorphism in the SFRS2 gene and detected a sequencing error, leading to an amino acid change (Val11Leu) in the published sequence of the putative sialyltransferase.