Comparative genetic analysis: the utility of mouse genetic systems for studying human monogenic disease

One of the long-term goals of mutagenesis programs in the mouse has been to generate mutant lines to facilitate the functional study of every mammalian gene. With a combination of complementary genetic approaches and advances in technology, this aim is slowly becoming a reality. One of the most important features of this strategy is the ability to identify and compare a number of mutations in the same gene, an allelic series. With the advent of gene-driven screening of mutant archives, the search for a specific series of interest is now a practical option. This review focuses on the analysis of multiple mutations from chemical mutagenesis projects in a wide variety of genes and the valuable functional information that has been obtained from these studies. Although gene knockouts and transgenics will continue to be an important resource to ascertain gene function, with a significant proportion of human diseases caused by point mutations, identifying an allelic series is becoming an equally efficient route to generating clinically relevant and functionally important mouse models

The Role of the Gap Junction Protein Connexin32 in the Myelin Sheath

X-linked Charcot-Marie-Tooth disease (CMTX) is caused by mutations in the gap junction gene connexin32 (Cx32). To date, 89 different mutations have been found, including deletions, insertions, missense, and nonsense mutations, and at least two mutations in the non-coding region. Different mutations appear to have different effects on the synthesis and localization of Cx32 protein. Both myelinating Schwann cells and oligodendrocytes express Cx32 mRNA and protein, and the localization of Cx32 protein matches the location of putative gap junctions previously seen by freeze-fracture electron microscopy. In myelinating Schwann cells, Cx32 protein is found in incisures and paranodes. Preliminary data suggest that gap junctions form a radial channel that directly traverses the myelin sheath. It is plausible that mutations in Cx32 disrupt the gap junctions in the myelin sheath, thereby abolishing this radial pathway and leading to peripheral neuropathy