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Someone may have posted this already but I missed it:

ANA: Impaired Gene Cluster Singled Out in Multiple Sclerosis

By Paula Moyer, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of Pennsylvania School of Medicine.
September 27, 2005

MedPage Today Action Points (this is aimed at doctors):

Explain to patients who ask that the genes of interest are the major histocompatibility complex (MHC) genes, which normally help discern autologous cells from bacteria and other pathogens.

This study was published as an abstract and presented orally at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.

Review
SAN DIEGO, Sept. 27-The most complete genetic study to date of multiple sclerosis singles out a cluster of genes on chromosome 6 as the only group to play a significant role in MS.

These findings, presented today at the annual meeting of the American Neurological Association, may constitute a turning point in the quest for an MS gene, according to principal investigator Jonathan Haines, Ph.D.

"No other region of the genome harbors a gene with a similar overall influence on MS genetics," said Dr. Haines in an oral presentation of the study. Dr. Haines is director of the Human Genetics Program at Vanderbilt University in Nashville, Tenn.

The genes that show so much promise are the major histocompatibility complex (MHC) genes, a cluster that enables the body to distinguish autologous cells from bacteria or other pathogens. When the MHC system is impaired, the body can develop antibodies against autologous cells, as in MS. An interaction between a variation in the MHC system and environmental challenges are the likely cause of MS, he said.

Noting that previous studies have implicated the MHC system, Dr. Haines distinguished the current research by the fact that for their linkage map, the researchers had access to a larger study population than had been used in prior MS genetics research.

The investigators typed 4,506 single nucleotide polymorphism markers found in 730 families in Australia, Scandinavia, the United Kingdom, and the U.S. Among these families were 945 affected relative pairs.

The investigators found a highly significant linkage in the MHC region. The mean information extraction in the study was 79.3%, suggesting that the findings were highly consistent, according to Dr. Haines. The observed Mendelian inconsistencies showed that, within the data set, the genotyping error rate was 0.002%.

The findings not only further implicate the MHC system but also show the need for larger data sets, Dr. Haines said. He suggested that future MS genetics research should include 500 to 1,000 cases.

Primary source: American Neurological Association. 130th annual meeting, September 25-28, 2005. San Diego, California. Abstract # WiP #4. Presented September 27, 2005.