Localization of the polymorphic human calcitonin gene on chromosome 11

Linkage map of the short arm of human chromosome 11: location of the genes for catalase, calcitonin, and insulin-like growth factor II

The following order of genes on the short arm of human chromosome 11 (11p) was determined previously: parathyroid hormone (PTH)-the beta-globin gene cluster (HBBC)-HRAS1/insulin. Although it is generally agreed that HRAS1 (formerly termed c-Ha-ras-1) and the insulin gene are close to each other [1-4 centimorgans (cM)], their order on chromosome 11p is still in question. We have now added three other genes, those for catalase, calcitonin, and insulin-like growth factor II (IGF-II), to this map of chromosome 11p by use of restriction site polymorphisms adjacent to these genes in classical linkage analysis. Most importantly, we find no evidence of linkage between the catalase and HBBC loci. In addition, our data indicate that the calcitonin gene is located between the catalase gene and the PTH gene. Our best estimate of the distance between the catalase and calcitonin gene is approximately 16 cM, while that between the calcitonin and PTH genes is approximately equal to 8 cM. In agreement, very loose linkage was found between the catalase and PTH loci (approximately 26 cM). Since the catalase locus has been mapped to 11p13, these data support the view that the PTH, HBBC, HRAS1, and insulin loci are located on the distal short arm of chromosome 11. The IGF-II gene is tightly linked to both the HRAS1 oncogene and the insulin gene since no recombinants were observed between the IGF-II and the HRAS1/insulin loci. Thus, based on our linkage analysis we propose that the most likely gene order for the short arm of chromosome 11 is centromere-catalase-calcitonin-PTH-HBBC-HRAS1/insulin-tel ome re and that the IGF-II gene is very close to both the HRAS1 and the insulin genes.

Assignment of human pepsinogen A locus to the q12-pter region of chromosome 11

A 0.9kb cDNA fragment, corresponding to a large part of Rhesus monkey pepsinogen A mRNA, was used as probe for the chromosomal localization of the human pepsinogen A gene(s) using human-rodent somatic cell hybrids. Southern blot analysis of 14 human-Chinese hamster and three human-mouse cell hybrids, strongly indicates that the human PGA locus is on chromosome 11. The human-mouse hybrids, containing a translocation involving chromosome 11, allow sublocalization to the region q12-pter.

Molecular analysis of gene deletion in aniridia--Wilms tumor association

Hybrid clones were produced from the fusion of Chinese hamster cells and human fibroblasts from a patient with the aniridia-Wilms tumor association (AWTA). The DNA from the parental cells and the hybrid clones was screened by Southern blot and DNA hybridization with probes for the human insulin and Ha-ras-1 genes. Two alleles for the Ha-ras-1 gene were shown to exist in the AWTA cells by restriction fragment length polymorphism. One hybrid clone, containing a single allele for Ha-ras-1 was shown to contain a single chromosome 11 with a cytogenetically visible deletion at 11p13. The DNA from this hybrid contained the human genes for insulin, A gamma-globin, G gamma-globin, Ha-ras-1, and calcitonin, but lacked any human sequences homologous to a human catalase cDNA. This clone was also shown to express human lactate dehydrogenase A (LDH A) activity. These data indicate that the deletion of the affected chromosome in this AWTA patient begins distal to LDH A and includes band 11p13, but does not extend to calcitonin or other genes thought to be located in the distal half of chromosome 11p.

A second human calcitonin/CGRP gene

The calcitonin (CT) gene is alternatively expressed in a tissue-specific fashion producing either the calcium regulatory hormone CT in the thyroid or the neuropeptide calcitonin gene related peptide (CGRP) in the brain. In medullary carcinoma of the thyroid both peptides are produced. We present here evidence for the existence in the human genome of a second CT gene, which is also expressed in human medullary thyroid carcinoma. This gene encodes a second human CGRP, differing from the known human CGRP in 3 of the 37 amino acids.

Novel peptides from the calcitonin gene: expression, receptors and biological function

Calcitonin gene products include calcitonin and its carboxyl-terminal flanking peptide (in man PDN-21), and calcitonin gene-related peptide (CGRP). Alternative splicing of the initial gene transcripts results in the production of two distinct messenger RNA encoding precursors of CGRP and of calcitonin. CGRP messenger RNA is the predominant transcription product of the calcitonin gene in neural tissues, but it is also present in the pituitary and the C-cells of normal thyroid glands and in medullary thyroid carcinoma. Immunoreactive CGRP has, moreover, been recognized around blood vessels of the heart. Calcitonin and PDN-21 are cosecreted from thyroid C-cells, but they are also found in the brain and pituitary. CGRP receptors are present in the brain and the heart, and calcitonin receptors in bone and kidney cells and in the hypothalamus. Calcitonin administered peripherally and in vitro inhibits bone resorption and stimulates renal 1.25-dihydroxycholecalciferol production. CGRP used in the same manner has potent cardiovascular effects (vasodilation, hypotension, positive chronotropic and inotropic action in the heart). Intracerebroventricular administration of CGRP raises the blood pressure, and both CGRP and calcitonin inhibit gastric acid secretion and food intake. The distinct but overlapping effects of calcitonin and CGRP raise important regulatory and functional issues.