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Insulin gene in diabetes. Analysis through RFLP
1Metabolism Division, Washington University School of Medicine, St. Louis, Missouri.
Diabetes Care
|March 1, 1990
Summary
Genetic studies of the insulin gene reveal no major role in diabetes mellitus (NIDDM, IDDM). While some associations exist for insulin-dependent diabetes mellitus (IDDM), a minor modifying role is suggested, requiring further investigation.
Area of Science:
- Genetics
- Molecular Biology
- Endocrinology
Background:
- Insulin deficiency is central to diabetes mellitus (NIDDM, IDDM).
- The human insulin gene has been cloned and mapped to chromosome 11.
- Restriction fragment length polymorphisms (RFLPs) near the insulin gene, including a variable number tandem repeat (VNTR) region, have been identified.
Purpose of the Study:
- To investigate the role of insulin gene defects in the pathogenesis of NIDDM and IDDM.
- To utilize RFLPs and VNTRs for genetic linkage and association studies in diabetic families.
Main Methods:
- DNA sequencing and RFLP analysis.
- VNTR typing for allele frequency determination.
- Family-based linkage analysis and association studies.
Main Results:
- Early studies suggested an association between specific VNTR alleles (approx. 170 copies) and NIDDM, but this was not consistently confirmed.
- Multiple studies demonstrated an association between different VNTR alleles (approx. 40 copies) and IDDM.
- Linkage analyses in families failed to establish a major role for insulin gene defects in NIDDM or IDDM in White and Black populations.
Conclusions:
- Insulin gene defects do not appear to play a major role in common forms of NIDDM or IDDM.
- A minor modifying role for the insulin gene in IDDM and potentially NIDDM cannot be excluded.
- Further direct investigation of the insulin gene in specific diabetic subsets using advanced techniques is warranted.