The chorionic gonadotropin alpha-subunit gene is on human chromosome 18 in JEG cells

First-trimester aneuploidy screening using serum human chorionic gonadotropin (hCG), free ahCG, and progesterone

Immunochemical serum assays for human chorionic gonadotropin (hCG), the free ahCG subunit, and progesterone (P) were considered separately and in combination for their ability to screen for chromosomally abnormal pregnancies in the first trimester. Maternal serum was collected from 141 women undergoing chorionic villus sampling at 9-12 menstrual weeks. Trisomy 21 pregnancies had significantly higher hCG levels, while trisomy 18 and 13 pregnancies had markedly lower hCG and progesterone levels than those of chromosomally normal pregnancies. However, the discrimination of normal from aneuploid pregnancies was poor with either hCG alone, progesterone alone, or free ahCG alone. Much improved discrimination was obtained by combining hCG, free ahCG, and P into an aneuploidy index [(P/hCG)(free ahCG/hCG)]. This index distinguished 9 out of 17 (53 per cent) of the trisomy 21 pregnancies, while only misidentifying 5 out of 112 (4.5 per cent) of the normal pregnancies. The aneuploidy index thus appears promising as a first-trimester biochemical screen for aneuploid pregnancies.

The molecular genetics of human chromosome 6

Chromosome 6 contains several clinically important markers as well as classical enzyme loci, proto-oncogenes, and a growing number of anonymous DNA restriction fragment length polymorphisms (RFLPs). It is also of unique interest because of the location of the major histocompatibility complex (MHC) on the short arm, at 6p21.3. The MHC is one of the most detailed areas of the human genetic map to date and many important diseases, some of a suspected autoimmune aetiology, are associated with it.

Assignment of the gene for the beta subunit of thyroid-stimulating hormone to the short arm of human chromosome 1

The chromosomal locations of the genes for the beta subunit of human thyroid-stimulating hormone (TSH) and the glycoprotein hormone alpha subunit have been determined by restriction enzyme analysis of DNA extracted from rodent-human somatic cell hybrids. Human chorionic gonadotropin (CG) alpha-subunit cDNA and a cloned 0.9-kilobase (kb) fragment of the human TSH beta-subunit gene were used as hybridization probes in the analysis of Southern blots of DNA extracted from rodent-human hybrid clones. Analysis of the segregation of 5- and 10-kb EcoRI fragments hybridizing to CG alpha-subunit cDNA confirmed the previous assignment of this gene to chromosome 6. Analysis of the patterns of segregation of a 2.3-kb EcoRI fragment containing human TSH beta-subunit sequences permitted the assignment of the TSH beta-subunit gene to human chromosome 1. The subregional assignment of TSH beta subunit to chromosome 1p22 was made possible by the additional analysis of a set of hybrids containing partially overlapping segments of this chromosome. Human TSH beta subunit is not syntenic with genes encoding the beta subunits of CG, luteinizing hormone, or follicle-stimulating hormone and is assigned to a conserved linkage group that also contains the structural genes for the beta subunit of nerve growth factor (NGFB) and the proto-oncogene N-ras (NRAS).

Assignment of the human tyrosine hydroxylase gene to chromosome 11

Using a panel of human-mouse somatic cell hydrids and a cDNA probe for human tyrosine hydroxylase, we have assigned the structural gene for tyrosine hydroxylase to chromosome 11 by Southern blotting techniques.

The beta chorionic gonadotropin-beta luteinizing gene cluster maps to human chromosome 19

We used a cloned human cDNA probe homologous to the placenta chorionic gonadotropin beta subunit (CGB) and to the pituitary luteinizing hormone beta subunit (LHB) and Southern blotting techniques to analyse DNA from a series of rodent X human somatic cell hybrids for the presence of specific gonadotropin beta subunit related sequences. Our results provide evidence for the assignment and linkage of the eight genes (or pseudogenes) coding for the beta subunit of these glycoprotein hormones to chromosome 19. Moreover, we observed a strict concordance between the permissivity of mouse X man hybrid cells to enteroviruses (which is linked to the presence of specific cell receptors encoded by human chromosome 19) and the presence of CGB and LHB related sequences, thus confirming the localization of the structural genes for the beta subunits on chromosome 19.

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.