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Genome-wide association studies have the potential to identify systematically the contributions of common genetic variants to human disease, but the tools to carry out such studies have been incomplete. Assessments of the HapMap resource suggest that the tools are now in hand, but care is required in their use for study design, analysis and interpretation.
The protein tyrosine phosphatase PTPN22 (also called LYP) is the leading example of a genetic variant that confers risk of developing diverse human autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, autoimmune thyroid disease and systemic lupus. A new study now shows that the PTPN22 risk-associated variant, Trp620, results in a gain of PTPN22 phosphatase activity in T cells, opening up new avenues for exploring disease mechanisms.
Mutations in SIL1, which encodes a nucleotide exchange factor for the chaperone BiP, cause a progressive multisystem disorder that probably results from abnormal protein quality control in the endoplasmic reticulum.
Although the correlation between maternal age and meiotic nondisjunction in human oocytes is widely recognized, the underlying molecular defects are largely unknown. New evidence from mice lacking SMC1β suggests that high levels of chromosome mis-segregation in older oocytes may be due in part to deterioration of meiotic sister-chromatid cohesion during aging.