Mutation analysis of the human adipocyte-specific apM-1 gene

The aim of this study was to analyse the human adipocyte-specific apM-1 gene for sequence variations.

Sequence analysis was performed in 344 randomly chosen blood samples using a capillary sequencer.

Whereas no mutations were detected in intronic regions and in 2.7 kb of the promoter, two sequence variations were found within the coding sequence of apM-1. For both mutations, a polymerase chain reaction-(PCR) based restriction fragment length polymorphism (RFLP) analysis was developed, which provided a rapid screening method. A conservative T --> G transition at nucleotide + 45 within exon-2 [Gly15Gly] was detected with an allelic frequency of 0.9 for the wild-type allele and 0.1 for the mutated allele. In addition, a missense point mutation at nucleotide + 331 within exon-3 [Tyr111His] was detected with an allelic frequency of 0.97 for the wild-type allele and 0.03 for the mutated allele. This mutation replaces a tyrosine by an histidine within the carboxyterminal globular domain of apM-1. Concerning the Gly15Gly polymorphism, the TT genotype was found in 275 subjects (79.9%), the TG genotype in 67 subjects (19.5%) and the GG genotype in 2 subjects (0.6%): one with maturity onset diabetes of young age (MODY-diabetes) and one with Lipoatrophic Diabetes Syndrome (LPDS). Concerning the Tyr111His polymorphism, the TT genotype was found in 328 subjects (95.4%), the TC genotype in 15 subjects (4.3%) and the CC genotype in 1 subject (0.3%).

The existence of two yet unknown mutations within the apM-1 gene was demonstrated and RFLP analysis was established for rapid screening. Well defined cohorts of patients are necessary to determine the putative role of apM-1 gene mutations in the pathogenesis of metabolic disorders.