Screening for insulin-like growth factor-I receptor mutations in patients with Silver-Russell syndrome

Individuals with a deletion of 15q26.1-->qter which contains the insulin-like growth factor-I (IGF-I) receptor gene exhibit phenotypical similarities to patients with Silver-Russell syndrome (SRS) who represent a group of short children affected by pre- and postnatal growth failure and several dysmorphic features. The genetic basis of SRS is presumably heterogeneous. The IGF-I receptor gene is a good SRS candidate gene because the biological effects of the major growth factors IGF-I and -II are transmitted through the IGF-I receptor during pre- and postnatal growth. All 12 patients studied exhibited the classical SRS phenotype with low birth weight, connatal macrocephaly, typical facial features and short stature at presentation. Klinodactyly of the fifth finger was found in ten patients, and skeletal asymmetry in seven. Chromosomal analysis gave normal results. Uniparental disomy of chromosome 7 was excluded. After reverse transcription of RNA, 19 overlapping cDNA fragments encompassing the whole IGF-I receptor coding sequence were PCR-amplified and screened for mutations by single strand conformation analysis (SSCP). In eight of 12 patients studied, we detected four SSCP polymorphisms which were directly sequenced. All single base exchanges (C948A, C2343T, G3174A and G3915A) were silent variants of the IGF-I receptor gene, two of which were also present in control individuals. In conclusion, for the first time, the complete coding region of the IGF-I receptor gene was screened for mutations in patients with SRS. Our data do not support the suggestion that the IGF-I receptor is frequently involved in the pathogenesis of SRS.