Growth hormone deficiency type IB caused by cryptic splicing of the GH-1 gene

We have found a novel mutation in intron 4 of the GH-1 gene in a Bedouin ki ndred with isolated growth hormone deficiency type IB (IGHD IB), RFLP analy sis suggested linkage between the GH-1 gene and IGHD. Nested PCR amplificat ion followed by single stranded conformation polymorphism (SSCP) analysis i ndicated sequence variation between introns 2 and 4, Sequencing showed a G- ->C transversion at the fifth base in the splice donor region of intron 4, Affected individuals were homozygous for the mutation, which creates a new Mae III restriction site. Reverse transcription and PCR of GH-1 transcripts in EBV transformed lymphocytes indicated predominance of a species lacking 73 bp of exon 4. Amplification with a bridging primer showed that the same mRNA species is present in lymphocytes from normal individuals. The first 102 amino acids of the predicted protein are identical to wild-type GH, but the next 94 amino acids are completely divergent.