De. Moller et al., PREVALENCE OF MUTATIONS IN THE INSULIN-RECEPTOR GENE IN SUBJECTS WITHFEATURES OF THE TYPE-A SYNDROME OF INSULIN-RESISTANCE, Diabetes, 43(2), 1994, pp. 247-255
Citations number
65
Categorie Soggetti
Endocrynology & Metabolism","Medicine, General & Internal
Mutations of the insulin receptor gene are a cause of the type A syndr
ome of extreme insulin resistance. This study assessed the prevalence
of such mutations in women with clinical features of the type A syndro
me including ovarian hyperandrogenism, moderate-to-severe degrees of i
nsulin resistance, and acanthosis nigricans. We studied 22 unrelated w
omen with insulin resistance (fasting insulin >300 pM [50 mu U/ml] and
/or peak during an oral glucose tolerance test (OGTT) >1,800 pM [300 m
u U/ml]), acanthosis nigricans, and the polycystic ovary syndrome (hyp
erandrogenemia, oligoamenorrhea, and hirsutism). Two insulin-resistant
probands with congenital generalized lipodystrophy and one male proba
nd with severe insulin resistance also were included in the study. Sou
thern blotting experiments were performed to exclude gross gene deleti
ons, insertions, or rearrangements. Exons 2-22 of the insulin receptor
gene were polymerase chain reaction (PCR) amplified from genomic DNA
and screened for nucleotide variation using single-strand conformation
polymorphism (SSCP). No nucleotide variation between study subjects w
as detected in exons 4-6, 10-12, 15, 16, 18, 19, or 21. Sequencing of
amplified DNA revealed that SSCP variants in exons 2, 3, 8, 9, and 17
corresponded to known silent polymorphisms within the coding region. V
ariants in exons 2, 9, 13, and 14 were caused by novel silent polymorp
hisms; variants in exons 7 and 22 were caused by nucleotide substituti
ons in flanking introns. One proband was found to have a heterozygous
point mutation in exon 20 (CGG-->CAG, Arg(174)-->Gln) that involves th
e intracellular receptor beta-subunit. Gln(1174) is a novel mutant of
the insulin receptor tyrosine kinase domain and is a likely cause of d
ominantly inherited insulin resistance. The mutation was present in an
affected sister but was absent in the unaffected mother and 64 normal
alleles. Two paternal aunts also are reportedly affected. The results
of this study suggest that mutations at the insulin receptor locus ar
e uncommon in insulin-resistant women with acanthosis nigricans and ov
arian hyperandrogenism.