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Insulin biosynthesis and diabetes mellitus
Clinical Biochemistry
|October 1, 1981
Summary
Recombinant DNA techniques reveal insights into insulin gene structure and regulation. DNA insertions near the human insulin gene are linked to type II diabetes, suggesting potential genetic markers.
Area of Science:
- Molecular Biology
- Genetics
- Endocrinology
Background:
- Insulin biosynthesis in pancreatic islet cells is primarily regulated by plasma glucose levels.
- Recombinant DNA technology allows for detailed study of gene structure and expression regulation.
- Insulin gene regulation involves complex mechanisms at the transcriptional and post-transcriptional levels.
Purpose of the Study:
- To review the application of recombinant DNA techniques in understanding human and animal insulin gene structure and expression.
- To investigate the role of DNA sequences and their variations in insulin gene regulation and their association with diabetes.
Main Methods:
- Utilized cell-free protein synthesizing systems to assay functional proinsulin messenger RNA (mRNA).
- Employed hybridization analysis with cloned DNA complementary to proinsulin mRNA.
- Isolated and sequenced insulin genes from rat, chicken, and human.
- Performed DNA hybridization analysis on mouse-human hybrid cells to determine human insulin gene location.
- Analyzed the structure of the human insulin gene in diabetic and non-diabetic individuals.
Main Results:
- Identified conserved sequences at the 5' ends of human, rat, and chicken insulin genes, indicating regulatory importance.
- Discovered two non-allelic insulin genes in rats, contrasting with single genes in chickens and humans.
- Characterized intervening sequences within insulin genes.
- Located the human insulin gene on chromosome 11.
- Detected DNA insertions (1500-3400 base pairs) near the transcription initiation site in 65% of type II diabetics versus 25-30% of non-diabetics (p < 0.001).
Conclusions:
- Changes in proinsulin mRNA levels are a key mechanism in insulin biosynthesis regulation.
- Structural similarities in insulin genes suggest conserved regulatory elements.
- DNA insertions near the insulin gene's promoter region may influence gene expression in type II diabetes.
- These specific DNA insertions represent potential genetic markers for diabetes.