Beta-globin locus is linked to the parathyroid hormone (PTH) locus and lies between the insulin and PTH loci in man

The parathyroid glands and parathyroid hormone: Insights from PTH gene mutations

Nine mutations have been discovered in the parathyroid hormone (PTH) gene since it was initially sequenced in 1983. An autosomal dominant C18R mutation in the signal peptide was first reported in 1990, followed by an exon skipping mutation, leading to loss of exon 2 in 1992; the latter mutation prevents PTH biosynthesis, as exon 2 contains the initiation codon. The S23P and S23X mutations affecting the same residue were reported in 1999 and 2012, respectively, while in 2008, the somatic mutation, R83X, was detected in a parathyroid adenoma tissue sample from a patient with overt hyperparathyroidism. In 2013, the heterozygous p.Met1_Asp6del mutation was discovered incidentally in a case-control study, while another heterozygous mutation, M14K, was detected in the signal peptide 4 years later. In 2015, a homozygous R56C mutation was reported, and was the first hypoparathyroidism-causing mutation identified that affects the mature bioactive portion of PTH; this mutation has significantly contributed to the understanding of the molecular mechanisms involved in signal transduction through the PTH receptor. Recently, a novel homozygous S32P mutation was identified, which is also situated in the bioactive portion of PTH. The discovery of these nine mutations in the PTH gene and determination of the molecular mechanisms underlying their effects has provided deep insights into the synthesis, processing, and secretion of PTH. Future attempts to discover other such mutations will help elucidate as yet unknown functions of PTH, with potential clinical implications.

Rare PTH Gene Mutations Causing Parathyroid Disorders: A Review

Since parathyroid hormone (PTH) was first isolated and its gene (PTH) was sequenced, only eight PTH mutations have been discovered. The C18R mutation in PTH, discovered in 1990, was the first to be reported. This autosomal dominant mutation induces endoplasmic reticulum stress and subsequent apoptosis in parathyroid cells. The next mutation, which was reported in 1992, is associated with exon skipping. The substitution of G with C in the first nucleotide of the second intron results in the exclusion of the second exon; since this exon includes the initiation codon, translation initiation is prevented. An S23P mutation and an S23X mutation at the same residue were reported in 1999 and 2012, respectively. Both mutations resulted in hypoparathyroidism. In 2008, a somatic R83X mutation was detected in a parathyroid adenoma tissue sample collected from a patient with hyperparathyroidism. In 2013, a heterozygous p.Met1_Asp6del mutation was incidentally discovered in a case-control study. Two years later, the R56C mutation was reported; this is the only reported hypoparathyroidism-causing mutation in the mature bioactive part of PTH. In 2017, another heterozygous mutation, M14K, was detected. The discovery of these eight mutations in the PTH gene has provided insights into its function and broadened our understanding of the molecular mechanisms underlying mutation progression. Further attempts to detect other such mutations will help elucidate the functions of PTH in a more sophisticated manner.

Genetic mapping by single sperm typing

The polymerase chain reaction makes it possible to analyse DNA sequences in a single cell and has led to a new approach for constructing genetic maps. We describe a procedure called 'sperm typing' which can accurately classify individual meiotic products as recombinant of non-recombinant. This permits the linkage relationships among DNA polymorphisms to be determined without pedigree analysis.

Molecular analysis of patients with Wiedemann-Beckwith syndrome. I. Gene dosage on the short arm of chromosome 11

Wiedemann-Beckwith syndrome (WBS) is characterised by a specific group of congenital malformations associated with an increased concurrent risk for development of a defined group of childhood neoplasms. The mode of inheritance is complex, but recently compiled family data suggest that it is an autosomal dominant trait of varying expression. It has previously been suggested that major rearrangements on the short arm of chromosome 11 may be involved in the aetiology of the disease, particularly in the region of the insulin like growth factor II (IGF-II) gene (11p15.5). This gene is thought to be parentally imprinted in the mouse and it has been suggested that in the human, duplication of the non-imprinted locus in WBS patient might lead to diploid expression of the gene and consequent general hyperplasia. This model predicts that there should be both frequent and parental origin specific duplication of the IGF-II gene in the patients. It was the aim of this study to examine the IGF-II locus and its surrounding chromosomal environment for such lesions in a large number of WBS patients. Using restriction fragment length polymorphism analysis for four linked markers on 11p and genomic clones internal to the IGF-II locus we could find no evidence of alteration or amplification of this area in any of the 11 patients investigated. In one patient who developed a Wilms tumour we could find no evidence for loss of any material on the short arm of chromosome 11 as reported previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of two novel polymorphisms at the human parathyroid hormone gene locus

Two new polymorphisms within the human parathyroid hormone (PTH) gene are described. One corresponds to a C----A transversion that destroys DraII and NlaIV restriction sites. The other is revealed by the enzyme XmnI, and its position has been mapped with respect to the PTH gene. We have also identified a sequence change that results in the TaqI restriction fragment length polymorphism (RFLP) described previously at this locus and have found that this sequence change also results in disruption of a BstBI site. Finally, we describe a polymerase chain reaction (PCR)-based method that permits a rapid evaluation of the DraII and BstBI (TaqI) polymorphisms. The introduction of these two additional RFLPs and this PCR-based assay should considerably extend the power of genetic analyses of the human PTH gene.

The molecular biology of parathyroid disease

Advances in molecular genetics have shed important new light on the understanding of the basis for human tumors. The application of these methods has allowed for characterization of endocrine neoplasms at a level of resolution that was not previously possible. A variety of molecular techniques have been applied to the study of parathyroid tumors at the DNA level. Studies of the clonal derivation of adenomas and hyperplasia suggest that these entities arise through fundamentally different mechanisms. The gene for parathyroid hormone (PTH) has been cloned and mapped within the human genome. In a small subset of parathyroid tumors, a rearrangement of the PTH gene has been described which may have contributed to their pathogenesis. A separate gene has been identified which appears to be responsible for the humoral hypercalcemia of malignancy. Chromosomal deletions which appear to be involved in the pathogenesis of multiple endocrine neoplasia type 1 have also been found in sporadic parathyroid adenomas. Characterization of tumors at the DNA level may make it possible to correlate specific genetic abnormalities with the biologic behavior of different parathyroid neoplasms and may be useful in distinguishing between adenoma, hyperplasia, and carcinoma.

Cloning and sequence analysis of the human parathyroid hormone gene region

A region of 50 kb around the human PTH gene was cloned and mapped by restriction analysis. Sequence analysis was performed and 3270bp determined, completing the sequence of the gene. The nucleotide sequence was analysed with regard to homology between human, bovine and rat PTH genes, and various potential cis-acting regulatory elements were identified. The gene region lacks an obvious CpG island. The PTH gene region in patients suffering from (pseudo)-hypoparathyroidism was investigated by Southern blotting. No detectable alteration in the fragment patterns was observed. Results of segregation analysis in families with affected individuals was inconclusive.

Single-sperm typing: determination of genetic distance between the G gamma-globin and parathyroid hormone loci by using the polymerase chain reaction and allele-specific oligomers

The frequency of recombination between the G gamma-globin (HBG2) and parathyroid hormone (PTH) loci on the short arm of human chromosome 11 was estimated by typing greater than 700 single-sperm samples from two males. The sperm-typing technique employed involves the polymerase chain reaction and allele-specific oligonucleotide hybridization. Our maximum likelihood recombination fraction estimate of 0.16 (95%) confidence interval, 0.13-0.19) falls well within previous estimates based on family studies. With current technology and a sample size of 1000 sperm, recombination fractions down to approximately 0.009 can be estimated with statistical reliability; with a sample size of 5000 sperm, this value drops to about 0.004. Reasonable technological improvements could result in the detection of recombination frequencies less than 0.001.

Genetic and synteny mapping of parathyroid hormone and beta hemoglobin in cattle

Parathyroid hormone and the beta hemoglobin gene cluster, which are closely linked on human chromosome 11p15, were localized to bovine syntenic group (U7) with the gene for catalase by the use of bovine x hamster hybrid somatic cells. Restriction fragment length polymorphisms (RFLPs) were followed through informative pedigrees to determine a linkage map distance of 15.6 +/- 5.4 cM between the parathyroid hormone and hemoglobin genes. Allelic frequencies of the DNA fragment were compared in a small sampling of cattle from five different breeds.

Analysis of gene dosage on chromosome 11 in children suffering from Beckwith-Wiedemann syndrome

The Beckwith-Wiedemann syndrome (BWS) is composed of multiple congenital malformations coupled with a high concurrent risk for the development of specific rare childhood tumours. The syndrome is characterised by a complex mode of inheritance, but recent evidence indicates that it is an autosomal dominant trait with variable penetrance. It has been previously suggested that major rearrangements of the short arm of chromosome 11 are involved in the aetiology of the disease. We undertook to search for rearrangements in 11p in four patients with BWS and their parents and siblings. By using cloned DNA fragments homologous to four genes located on 11p, namely catalase, parathyroid hormone, insulin-like growth factor II and the proto-oncogene c-Ha-Ras, we subjected DNA from the patients to a restriction fragment length polymorphism (RFLP) analysis after digestion with restriction enzymes. We found no evidence for any large scale deletions or amplifications in this chromosomal region. We therefore conclude that altered gene dosage is not, as has been suggested, a requirement for the development of BWS. This raises the question of whether some other molecular mechanism is responsible for the malformations observed.

Molecular nature of genetic changes resulting in loss of heterozygosity of chromosome 11 in Wilms' tumours

In this paper we describe the analysis of genetic changes in chromosome 11 in Wilms' tumours. Using a range of probes for regions 11p15, 11p13 and 11q we have screened DNA from 14 Wilms' tumours together with control DNA obtained from the patients' lymphocytes and their parents. We have been able to demonstrate loss of heterozygosity in 5 of the 14 different Wilms' tumours. In three of these five tumours, loss of heterozygosity did not involve markers for 11p13, 11p15.4 or the proximal region of 11p15.5, but only some markers assigned to the most distal part of 11p15.5. In two of these tumours we could demonstrate unequal mitotic recombination in 11p with breakpoints in the hypervariable regions 5' of the insulin gene and/or 3' of the HRASI proto-oncogene. In one tumour, from a Beckwith-Wiedemann patient, all markers for the region 11q13-pter became hemizygous; the region 11q13-qter remained heterozygous. These results demonstrate that loss of heterozygosity in Wilms' tumours may not necessarily involve the proposed Wilms' tumours locus at 11p13 but may be limited to 11p15.5. This suggests that not only the 11p13 region, but also the 11p15.5 region is involved in Wilms' tumour development. The possible role of both regions in the development of Wilms' tumour is discussed.

The development of medullary carcinoma of the thyroid does not involve the loss of alleles on the short arm of chromosome 11

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Regional localization of DNA probes on the short arm of chromosome 11 using aniridia-Wilms' tumor-associated deletions

We are interested in the precise localization of various DNA probes on the short arm of chromosome 11 for our research on the aniridia-Wilms' tumor association (AWTA), assigned to region 11p13 (Knudson and Strong 1972; Riccardi et al. 1978). For this purpose we have screened lymphocyte DNA and material derived from somatic cell hybrids from individuals with constitutional 11p deletions with a range of available probes: D11S12; calcitonin/CGRP (CALC1/CALC2); insulin (INS); Harvey ras 1 (HRAS 1); beta-globin gene cluster (HBBC); human insulin-like growth factor 2 (IGF-2); parathyroid hormone (PTH); human pepsinogen A (PGA). Using this material, it has been possible to map all probes used, except insulin, outside the region 11p111-p15.1, resulting in an SRO (same regional overlap) of 11p15.1-p15.5 for most probes. We found an SRO for PGA of 11p111-q12 and an SRO for CALC2 of 11p15.1-p15.5 or 11p111-q12. We have localised the insulin gene to band 11p15.1.

Gamma delta beta-thalassaemias 1 and 2 are the result of a 100 kbp deletion in the human beta-globin cluster

The DNA spanning two large deletions in the human beta-globin gene cluster (gamma beta-thalassaemia 1 and 2) has been cloned by cosmid cloning and chromosomal walking. The entire region was mapped and analyzed for the presence of repetitive sequences. The results show that the affected loci have lost almost 100 kb of DNA in a deletion event not involving homologous or repetitive sequences.

Exclusion of close linkage between the parathyroid hormone gene and a mutant gene locus causing idiopathic hypoparathyroidism

A family is presented in which the mother has transmitted primary hypoparathyroidism with early onset and serum PTH (44-68) and C terminal deficiency to her two sons. Restriction enzyme analysis of allelic variation at the PTH gene locus revealed that the disease and the PTH alleles segregate independently. It is therefore concluded that the primary molecular defect leading to this form of hypoparathyroidism is not located within the PTH gene itself.

Construction of human linkage maps: likelihood calculations for multilocus linkage analysis

Methods are given for efficient calculation of the likelihood for multilocus linkage in families comprised of grandparents, parents, and children. Such families are being used in large-scale cooperative efforts to build a detailed linkage map of the human genome. The methods are illustrated by an application to loci on chromosome 13.

Molecular biology of parathyroid hormone

The entire biosynthetic pathway of PTH has been elucidated from the determination of the chromosomal location to the eventual secretion of the hormone from the cell. The human gene is present on the short arm of chromosome 11, and restriction site polymorphisms near the gene have been detected. The PTH genes and cDNAs have been isolated and characterized in the bovine, human, and rat species. The gene contains two introns, which are in the same position in each species, and dissect the gene into 3 exons that code, respectively, for the 5' untranslated region, the signal peptide, and PTH plus the 3' untranslated region. The mRNAs are about twice as long as necessary to code for preProPTH and contain a 7-methylquanosine cap at the 5' terminus and polyadenylic acid at the 3' terminus. The 5' termini of the bovine and human mRNAs are heterogeneous at the 5' terminus, the basis of which is two TATA sequences in the 5' flanking regions of the gene. In contrast, the rat gene contains a single TATA sequence and the mRNA has a single 5' terminus. The initial translational product of the mRNA is preProPTH, and the pre-peptide of 25 amino acids is equivalent to signal peptides of other secreted and membrane proteins. The genes of the three species are very homologous in the region that codes for preProPTH. Substantial homology is also retained in the gene flanking regions, introns, and mRNA untranslated regions. Silent sites are also conserved more than would be expected, particularly between the human and bovine sequences. The bovine and human sequences are more closely related than the rat is to either the human or bovine. These studies of the basic molecular biology of PTH will provide the framework for future analysis of significant biological and medical questions. In vitro mutagenesis techniques should soon provide information about the elements of the gene involved in regulating transcription and about functional elements of the signal peptide. Eventually, signals involved in directing the ProPTH molecule to secretory granules as well as the biologically active regions of PTH, itself, will be examined by these methods. The molecular biological studies, combined with the development of dispersed cell cultures, provide the opportunity to study the effects of chronic changes in calcium on gene transcription and mRNA metabolism. The restriction site polymorphisms associated with the human PTH gene will allow a search for correlations between PTH gene structure and parathyroid disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular analysis of chromosome 11 deletions in aniridia-Wilms tumor syndrome

We describe five individuals who have constitutional deletions of the short arm of one chromosome 11, including all or part of the band p13. All of these individuals suffer from aniridia; two have had a Wilms tumor removed. We have established lymphoblastoid cell lines from these and in three cases constructed somatic cell hybrids containing the deleted chromosome 11. Analysis of DNA from the cell lines and hybrids with a cloned cDNA probe has shown that the catalase gene is deleted in four of five patients. The catalase locus must be proximal to the Wilms and aniridia-related loci. We have not detected a deletion of the beta-globin or calcitonin genes in any of these individuals; we conclude these genes are likely to be outside the region 11p12-11p15.4. In addition, we have used monoclonal antibodies in fluorescence-activated cell sorting analysis to measure expression in the hybrids of two cell surface markers encoded by genes that map to the short arm of chromosome 11. The genes for both of these are deleted in two individuals but are present in the individual with the smallest deletion.

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.

A mitotic recombination in Wilms tumor occurs between the parathyroid hormone locus and 11p13

Wilms tumor is believed to occur as the result of two mutations affecting both alleles of a critical gene located within the p13 band of chromosome 11 (Knudson and Strong 1972; Riccardi et al. 1978). Several mechanisms by which these mutations occur have already been determined in retinoblastoma (Cavenee et al. 1983) and Wilms tumor (Koufos et al. 1984; Orkin et al. 1984; Reeve et al. 1984; Fearon et al. 1984a; Eccles et al. 1984). Of the various mechanisms, however, no example of a mitotic recombination was demonstrated in Wilms tumor. An example is presented here which has been detected by the use of restriction fragment length polymorphisms (RFLPs) mapping to chromosome 11p. In addition the data presented are consistent with the mapping location of parathyroid hormone (PTH) being proximal to 11p13.

A systematic approach for detecting high-frequency restriction fragment length polymorphisms using large genomic probes

Thirteen phage clones containing low-copy sequences were isolated from a human DNA library and tested for their ability to detect restriction fragment length polymorphisms (RFLPs). Reported are the RFLPs revealed with each clone, all found in frequencies useful for linkage studies. Cytological data are available for five of the 13 clones, with regional assignments made for three of the markers by in situ hybridization. It is concluded that phage clones containing large unique DNA inserts detect multiple RFLPs with high efficiency. An analysis of the relative efficiency of 20 restriction enzymes for detecting single nucleotide changes is discussed by comparing the observed data to those expected on the basis of recognition and potential site frequencies, as computed from the dinucleotide distribution. Finally, in an effort to facilitate linkage studies using polymorphic DNA sequences, experiments were made with pools of probes from various sources.

The second human calcitonin/CGRP gene is located on chromosome 11

A second human calcitonin/calcitonin gene related peptide (hCT/CGRP) gene has been identified. This second hCT/CGRP gene has been shown to contain sequences highly homologous to exons 3, 5 (CGRP-encoding), and 6 of the first hCT/CGRP gene, but sequences closely related to exon 4 (CT-encoding) could not be demonstrated. Southern blot hybridization analysis of DNA from human-rodent somatic cell hybrids showed that the second hCT/CGRP gene is located in the q12-pter region of chromosome 11. The first hCT/CGRP gene has previously been assigned to the p13-p15 region of chromosome 11.

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.

Multilocus linkage analysis in humans: detection of linkage and estimation of recombination

Multilocus linkage analysis is investigated from the viewpoint of the efficiency of recombination estimates under different strategies for detecting linkage and determining gene order within a linkage group. We consider the appropriateness of assuming no interference with data available in human genetic studies. Examples are given to show the significance of multilocus analysis in humans. A computer program package, LINKAGE, for multilocus linkage analysis is described.

The telomeric region of the human X chromosome long arm: presence of a highly polymorphic DNA marker and analysis of recombination frequency

A DNA fragment (named St14) derived from the human X chromosome reveals a small family of related sequences that have been mapped to the Xq26-Xq28 region by using a panel of rodent-human somatic cell hybrids. The probe detects in human DNA digested by Taq I a polymorphic system defined by a series of at least eight allelic fragments with a calculated heterozygosity in females of 80%. With Msp I, we found three additional restriction fragment length polymorphisms, each of them being defined by two alleles. These polymorphisms are also common in Caucasian populations. The genetic locus defined by probe St14 has been localized more precisely to the distal end of the X chromosome (in band q28) by linkage analysis to other polymorphic DNA markers. The results obtained suggest that the frequency of recombination is distributed very unevenly in the q27-qter region of the X chromosome, with a cluster of seven tightly linked loci in q28 showing about 30% recombination with the gene for coagulation factor IX located in the neighboring q27 band. Probe St14 reveals one of the most polymorphic loci known to date in the human genome, and 17 different genotypes have already been observed. It constitutes the best marker on the X chromosome and should be of great use for the genetic study of three important diseases: hemophilia A, mental retardation with a fragile X chromosome, and adrenoleukodystrophy.

Localization of the beta-globin gene to 11p15 by in situ hybridization: utilization of chromosome 11 rearrangements

Chromosome preparations from four subjects, one normal 46,XY male and three patients with different rearrangements of chromosome 11: 46,XX,del(11)(p11.2----p15.1), 46,XY,inv(11)(p13q24.2), and 46,XY,rec(11)inv(11)(p13q24.2) pat, were utilized for in situ hybridization studies with a tritium-labeled cDNA probe containing a beta-globin insert. Using the hybridization technique described by Harper and Saunders (1981), there were 1-2 grains over each labeled metaphase. Of 360 cells scored, 88 were labeled over chromosome 11, band p15 (24%). Approximately half of the chromosome 11s labeled from the abnormal patients were the del(11) or inv(11). These results exclude the beta-globin locus from 11p11----p14, since these bands were not present in the deleted 11, and assign it to 11p15. This is in agreement with the recent exclusion data of de Martinville and Francke (1984) and Junien (1984), and suggestive assignment data of Morton et al. (1984).

Germ-line chromosomal localization of genes in chromosome 11p linkage: parathyroid hormone, beta-globin, c-Ha-ras-1, and insulin

The chromosomal localization of genes for parathyroid hormone (PTH), beta-globin cluster, c-Ha-ras-1, and insulin, all of which have previously been assigned to the short arm of chromosome 11, generated considerable interest because of their association with development of disease states. Furthermore, the availability of recombination data from family studies made the determination of their physical location on the chromosome necessary. Several investigators have attempted this; however, controversy has arisen concerning the location of beta-globin, insulin, and c-Ha-ras-1 genes. Thus, while the results of some investigators suggested that all three genes are situated in the 11p15 region, data of other investigators placed the beta-globin and insulin genes close to the centromere and c-Ha-ras-1 in a more proximal region than 11p15. The subchromosomal position of the PTH gene remains to be determined. We have performed in situ hybridization of meiotic pachytene bivalents with 3H-labeled cloned genomic probes of PTH, beta-globin, and insulin genes and find their germ-line positions to be the following: PTH at 11p11.21, beta-globin at 11p11.22, and insulin at 11p14.1. These data, when considered with our recent germ-line assignment of the c-Ha-ras-1 gene to 11p14.1, indicate the following relative order on 11p: cen-PTH-beta-globin-c-Ha-ras-insulin or cen-PTH-beta-globin-insulin-c-Ha-ras. The former order is consistent with genetic evidence from linkage analysis of DNA polymorphisms adjacent to these genes segregating in families.

Identification of a recent recombination event within the human beta-globin gene cluster

In a detailed study of inheritance of DNA sequence polymorphism in a large reference pedigree, an individual was identified with an apparent genetic recombination event within the human beta-globin gene cluster. Analysis of the haplotypes of relevant individuals within this pedigree suggested that the meiotic crossing-over event is likely to have occurred within a 19.8-kilobase-pair region of the beta-globin gene cluster. Analysis of other DNA markers closely linked to the beta-globin gene cluster--segment 12 of chromosome 11 (D11S12) and loci for insulin, the cellular oncogene c-Ha-ras, and preproparathyroid hormone--confirmed that a crossover event must have occurred within the region of chromosome 11 between D11S12 and the beta-globin gene cluster. It is suggested that the event observed has occurred within a DNA region compatible with recombinational "hot spots" suggested by population studies.

Restriction fragment length polymorphisms at the human parathyroid hormone gene locus

Two common Pst I and Taq I restriction enzyme fragment length polymorphisms (RFLPs) were detected at the human parathyroid hormone (PTH) gene locus. The allele frequencies in a Northern German population were 0.578/0.422 (Pst I) and 0.628/0.372 (Taq I). The allele distributions follow Hardy-Weinberg expectations of equilibrium in the population. The Mendelian nature of the polymorphisms were confirmed in family studies.

Somatic deletion and duplication of genes on chromosome 11 in Wilms' tumours

One of the most provocative findings in tumour biology is the relationship between chromosomal changes and embryonal cancers in children. For example, children with the rare paediatric syndrome AGR triad (aniridia, genito-urinary abnormalities and mental retardation) often develop Wilms' tumours at a very early age and carry a germ-line deletion on the short arm of chromosome 11 (11p13). It has been suggested that the germ-line deletion 11p is the first of two or more steps to cancer in AGR children. If this were true, one might expect a similar deletion to arise somatically in the far more common isolated Wilms' tumours of children without AGR, as suggested by Knudson from epidemiological data. However, a chromosomal deletion on 11p was observed in only two of five such cases, while it was absent or seen inconsistently in others. We have now used a molecular genetic approach to determine whether Wilms' tumour cells possess somatic alterations at 11p loci. We have found somatic deletions of specific genes in four of six Wilms' tumours. Surprisingly, in all four cases, the deletions were associated with duplications leading to homozygosity of the non-deleted alleles in the tumour cells. As analogous observations were recently reported in retinoblastoma, the genetic events reported here may underlie the development of many such embryonal tumours in children.

Genetic mapping of the human X chromosome by using restriction fragment length polymorphisms

Using a human X chromosome-specific DNA library, we have found arbitrary single-copy DNA sequences that reveal useful restriction fragment length polymorphisms. The inheritance of these and other available polymorphic DNA markers has been studied in a series of unrelated three-generation families with large sibships. These families reveal parental phase and allow determination of recombination frequencies by counting recombinant and nonrecombinant chromosomes. The resulting genetic map indicates that the minimal distance from Xp22 to Xqter is 215 recombination units. The spacing of the marker loci is such that the majority of the loci on the X chromosome, including disease loci, will lie within 20 centimorgans of at least one of these loci.

Localization of the beta-globin gene by chromosomal in situ hybridization

A 3.7-kilobase (kb) genomic clone of the human beta-globin gene, including 1.5-kb upstream and approximately 0.5-kb downstream, was utilized in chromosomal in situ hybridization for precise mapping of the beta-globin locus on peripheral blood lymphocyte-derived metaphases from a normal male, and for further evaluation of a clonal t(7;11) (q22;p15) translocation on bone marrow-derived metaphases from a 46-year-old male with erythroleukemia. Analyses of 205 midmetaphases from a normal male hybridized with the tritium-labeled beta-globin probe and stained with quinacrine mustard dihydrochloride revealed approximately 12% of spreads to have silver-grain deposition over the p15 band of chromosome 11. Of the 365 silver grains observed to be located on or beside chromosomes, 25 (approximately 7%) grains were localized in band p15. Karyotype analysis of a bone marrow specimen from the patient with erythroleukemia revealed hypodiploidy with various unidentified marker chromosomes as well as a presumably balanced translocation between 7q and 11p . Chromosomal in situ hybridization showed localization of silver grains at the junction between chromosomes 7 and 11 as well as to the normal chromosome 11, indicating that the beta-globin locus had not been translocated in the chromosomal rearrangement. This case demonstrates the value of chromosomal in situ hybridization in the definition of chromosome rearrangements and provides further evidence for the localization of the beta-globin gene to 11p15 .

c-Ha-ras-1 oncogene lies between beta-globin and insulin loci on human chromosome 11p

DNA sequence polymorphisms have been used to determine the linear order and recombinational distances separating the Harvey ras 1 oncogene (c-Ha-ras-1), beta-globin, insulin, and parathyroid hormone genes on the short arm of human chromosome 11. Our results indicate that c-Ha-ras-1 is closely linked to both the beta-globin locus (theta = .08 [8 centimorgans], lod score = 5.11) and the insulin locus (theta = .04 [4 centimorgans], lod score = 3.31). Furthermore, the probable order of these loci on chromosome 11p is centromere-parathyroid hormone-beta globin-c-Ha-ras-1-insulin.