Eukaryotic pre-mRNA splicing is regulated by consensus sequences at the intron boundaries and branch site. Recently, Sirand-Pugnet et al. reported the importance of an additional intronic sequence, an (A/U)GGG repeat in chicken beta-tropomyosin that is a binding site for a protein required for spliceosome assembly. Interestingly, we have detected mutations in IVS3 of the human growth hormone (GH) gene that affect a putative, homologous consensus sequence and which also perturb splicing. In a series of dominant-negative GH mutations that cause exon skipping, we found two mutations that do not occur within the 5' and 3' splice sites, or branch consensus sites. The first mutation is a G-->A transition of the 28th base (+28G-->A) of and the second deletes 18 bp (del+28-45) of IVS3 of the human GH gene. These mutations segregated with autosomal dominant GH deficiency in both kindreds and no other allelic GH gene changes were detected. RT-PCR amplification of transcripts from expression vectors containing the +28G-->A or del+28-45 alleles yielded products showing a >10-fold preferred use of alternative splicing, similar to findings previously reported for IVS3 donor site mutations. Both mutations are located 28 bp downstream from the 5' splice site and examination of the sequences perturbed revealed an intronic XGGG repeat similar to the repeat found to regulate mRNA splicing in chicken beta-tropomyosin. Interestingly, the XGGG repeats involved in our mutations exhibit homologous spacing to those in a so-called 'winner' RNA sequence. Binding of A1 heterogeneous nuclear ribonucleoprotein (hnRNP) by 'winner' sequences in pre-mRNA transcripts is thought to play an important role in pre-mRNA packaging and transport as well as 5' splice site selection in pre-mRNAs that contain multiple 5' splice sites. Our findings suggest that (i) XGGG repeats may regulate alternative splicing in the human GH gene and (ii) mutations of these repeats cause GH deficiency by perturbing alternative splicing. Mutations of homologous intron sequences may underlie other human diseases.

Objective: To examine the prevalence and risk factors of vitamin deficiencies among older Thai adults. Methods: The cross-sectional study was conducted in four rural communities, one from each of the four main regions of Thailand. In total, 2336 subjects aged 60 years and over were recruited. Anthropometric variables, demographic data, blood glucose and lipid profile, albumin, globulin and blood levels of vitamin A, b-carotene, folic acid, vitamin B 12 , vitamin C, vitamin E and vitamin B 1 were all measured. Results: The prevalence of vitamin deficiencies was 0.6% for vitamin B 12 , 6.1% for vitamin A, 9.9% for vitamin C, 30.1% for vitamin B 1 , 38.8% for erythrocyte folate, 55.5% for vitamin E and 83.0% for b-carotene. Male gender was a common risk factor for at least three vitamin deficiencies, i.e. b-carotene, folate and vitamin E. Being a manual worker was a common risk factor of b-carotene and vitamin B 1 deficiency. Poor income was found as a risk factor only in erythrocyte folate deficiency while increasing age was a significant factor only in vitamin C deficiency. Conclusion: The prevalence of vitamin deficiencies among older Thai people was quite different from that found in Western countries, reflecting different socioeconomic backgrounds. Vitamin deficiency was not only from poor food intake but also from the dietary habit of monotonous food consumption in older people. Some common associated factors of atherosclerosis were also significantly related to folate and vitamin E deficiencies.

Autosomal dominant familial isolated growth hormone (GH) deficiency (IGHD type II) is a rare cause of human GH deficiency. Virtually all reported instances have been due to mutations of the GH gene (GH1) donor splice site at the junction of exon 2 and intron 3 (intervening sequence 3, or IVS3). The biological mechanisms by which such mutations of a single allele result in a functional deficiency state {i.e. dominantnegative effects on the normal allele) have not been elucidated. Here we report four unrelated families with IGHD type II caused by a novel missense transition mutation, G6664A, which replaces arginine at position 183 with histidine (Argl83His, or R183H) in exon 5 of GH1. KEY WORDSshort stature, autosomal dominant, isolated growth hormone deficiency (IGHD) type II, hot-spot, CpG dinucleotide