Genetic Mutations, Birth Lengths, Weights and Head Circumferences of Children with IGF-I Receptor Defects. Comparison with other Congenital Defects in the GH/IGF-I axis.

BACKGROUND: In recent years more and more genetic defects along the GHRH-GH-IGF-I axis have been reported. Mutations of the IGF-I receptor (R) are a rare abnormality of whom only the heterozygote progenies survive. OBJECTIVES: To summarize, from the literature, data on birth length, weight and head circumference of neonates with IGF-I-R mutations, and to correlate the data with that of other types of mutations in the GH/IGF-I axis. SUBJECTS: Sixty seven neonates from 24 published articles were included and forty seven different mutations of the IGF-I (R) located on chromosome 15 have been identified. RESULTS: Mean (±SD) birth length (BL), available for 26, (10 M, 16F) neonates with a gestational age of 34-41weeks, was 44.2±4cm; one was premature (30cm at 31 weeks). There was a significant correlation between birth length and gestational age (GA) r=0.71 (p>.001). Mean birth weight (BW) of 41 neonates (18M, 23F) was 2388±743gr. Two premature neonates weighed 650gr and 950gr respectively. The BW correlated significantly with gestational age, (males: r=0.68; p=0.007, females: r=0.49; p=0.024). The BMI of 25 neonates ranged from 6 to 13. In 22 records marked microcephaly was ascertained or stated. Nine of 16 mothers were short (133 -148cm), m±SD = 150.5±7.3cm.

Homozygous MED25 mutation implicated in eye-intellectual disability syndrome.

Genetic syndromes involving both brain and eye abnormalities are numerous and include syndromes such as Warburg micro syndrome, Kaufman oculocerebrofacial syndrome, Cerebro-oculo-facio-skeletal syndrome, Kahrizi syndrome and others. Using exome sequencing, we have been able to identify homozygous mutation p.(Tyr39Cys) in MED25 as the cause of a syndrome characterized by eye, brain, cardiac and palatal abnormalities as well as growth retardation, microcephaly and severe intellectual disability in seven patients from four unrelated families, all originating from the same village. The protein encoded by MED25 belongs to Mediator complex or MED complex, which is an evolutionary conserved multi-subunit RNA polymerase II transcriptional regulator complex. The MED25 point mutation is located in the von Willebrand factor type A (MED25 VWA) domain which is responsible for MED25 recruitment into the Mediator complex; co-immunoprecipitation experiment demonstrated that this mutation dramatically impairs MED25 interaction with the Mediator complex in mammalian cells.