Introduction to MVR-PCR at the insulin minisatellite

Minisatellites are composed of tandem repeats 10-100 bp in length, with total array sizes of typically 0.5-50 kb. Polymorphisms exist between tandem repeats generating variant repeat types. The interspersion patterns of variant repeats within alleles can be analysed by PCR amplification between a universal primer which anneals outside of the repeat array, and primers which binds to specific variant repeats within the array. This technique is called minisatellite variant repeat mapping by PCR, or MVR-PCR.

A system of MVR-PCR was developed at the insulin minisatellite to detect 6 different variant repeats, the sequences of which are as follows with nucleotides that differ from the A-type repeat consensus underlined:

This technique was used to type variant repeat distributions within 876 alleles from 219 type 1 diabetes affected sib pair families, the results of which may be viewed here:

Allele diversity at the insulin minisatellite

In addition, de novo mutants at this locus were detected in sperm DNA of three donors, and from blood DNA of the first donor. All mutant structures detected may be viewed here:

Mutation analysis at the insulin minisatellite

In each case, letters within MVR-PCR codes represent different variant repeat types as described above. 'o' represents null repeats (unamplifiable repeats due to the presence of polymorphisms which prevent binding of any of the repeat-specific primers). Hyphens are inserted to facilitate alignment of alleles.

In the allele diversity study, allele names represent the lineage to which each allele belongs, repeat number, and a further discriminating number. For example, allele ID42.4 is the 4th allele of 42 repeats in length identified within lineage ID. Alleles of lineage IIIA divide into two further subgroups, IIIAi and IIIAii. IIIAii alleles are indicated by *. The number of copies of each allele detected in this study is indicated.

The names of mutant structures detected reflect the DNA source (B for blood DNA, S for sperm DNA) and the donor from which the sample was derived, repeat number and a further discriminator. For example, S1-38.5 was the 5th mutant 38 repeats in length, detected from sperm DNA of donor 1. Multiple copies of some mutant structures were detected as indicated by *. Some mutants are divided over several lines to improve alignment of the mutants with the progenitor alleles.

These pages provide supplementary information for the following publications:

Global haplotype diversity in the human insulin gene region. Stead, J.D.H., Hurles, M.E. and Jeffreys, A.J. Genome Res. 13, 2101-11 (2003)

Structural analysis of insulin minisatellite alleles reveals unusually large differences in diversity between Africans and non-Africans. Stead, J.D.H. and Jeffreys, A.J. Am. J. Hum. Genet. 71, 1273-84 (2002)

Influence of allele lineage on the role of the insulin minisatellite in susceptibility to type 1 diabetes. Stead, J.D.H., Buard, J., Todd, J.A. and Jeffreys, A.J. Hum. Mol. Genet., 9, 2929-2935 (2000).

Allele diversity and germline mutation at the insulin minisatellite. Stead, J.D.H. and Jeffreys, A.J. Hum. Mol. Genet., 9, 713-723 (2000).