M. Bobrow

Chromosome assignment of some human enzyme loci: mitochondrial malate dehydrogenase to 7, mannosephosphate isomerase and pyruvate kinase to 15 and probably, esterase D to 13.

Eleven independent man-mouse hybrids and 40 subclones from four to them were analysed for up to 42 enzyme markers. Nine subclones from three hybrid lines were fully karyotyped. The data presented suggest that the gene for the human enzyme MOR-M can be assigned to chromosome 7, whilst those for MPI and PK-3 are on chromosome 15. The use of a small number of well-characterized hybrids for gene assigments is discussed as well as the significance of some known human linkage relationships.

Human gene mapping using an X/autosome translocation.

Human fibroblasts containing a translocation between the X chromosome and chromosome 15 were fused with the 6-thioguanine-resistant mouse cell line, IR. Resulting hybrids, selected in HAT medium, retained the X/15 chromosome. Hybrids which were counterselected in 6-thioguanine lost this chromosome. The X-linked markers glucose-6-phosphate dehydrogenase (G6PD), phosphoglycerate kinase (PGK), and hypoxanthine phosphoribosyl transferase (HPRT), and the non-X-linked markers pyruvate kinase (PKM2) mannose phosphate isomerase (MPI), N-acetyl hexosaminidase A (HEXA) and β2-microglubulin (β2-m) all segregated in concordance with the X/15 translocation chromosome. The latter markers have been assigned to chromosome 15. Selection against the X/15 chromosome was done using antihuman β2-m serum. Electrophoretic and immunochemical analyses of the N-acetyl hexosaminidases A and B in these hybrids were performed.

Generation of novel sequence tagged sites (STSs) from discrete chromosomal regions using Alu-PCR.

Human DNA segments from discrete chromosomal regions were generated by utilizing Alu-element-based polymerase chain reaction (Alu-PCR) of an irradiation-fusion hybrid containing approximately 10 to 15 Mb of human DNA. Following cloning into a plasmid vector, a subset of the clones was used to generate sequence tagged sites (STSs) de novo. By means of a panel of hybrids containing portions of the human X chromosome, the STSs were shown to localize to two chromosomal regions, Xq24-Xq26 and Xcen-Xq13, reflecting the presence in the irradiation-fusion hybrid of two human chromosome fragments. These results demonstrate that high densities of STSs can be rapidly and efficiently generated from defined regions of the human genome using Alu-PCR.

The identification of a repeated DNA sequence involved in the karyotype polymorphism of the human Y chromosome

We show that individual men are polymorphic for the amount of two different repeated DNA sequences. The amount of one of these sequences is proportional to the length of the brightly fluorescent heterochromatin on the Y chromosome. There are no detectable alterations in sequence between polymorphic individuals. Female DNA contains sequences complementary to those found on the Y, but at a much reduced level.

Assignment of the human locus determining phosphoglycolate phosphatase (PGP) to chromosome 16

The segregation of human phosphoglycolate phosphatase has been studied in 52 independent human-rodent hybrids and 69 subclones. The results suggest that human PGP is on chromosome 16. Family data suggest that PGP is not close to 16qh or alpha Hp. The most likely regional assignment for PGP would appear to be 16p13 or 16p12, but a site on 16q cannot be entirely excluded. New data on 16qh and alpha Hp suggest that the male recombination fraction between these loci is about 0.2.

X inactivation as a mechanism of selection against lethal alleles: further investigation of incontinentia pigmenti and X linked lymphoproliferative disease.

Thirty-one females with incontinentia pigmenti (IP), 42 controls, and 11 females from four families segregating for X linked lymphoproliferative disease (XLP) were studied for evidence of skewed X inactivation by analysis of methylation at sites in the HPRT, PGK, and M27 beta (DXS255) regions of the X chromosome. Extensive skewing of X inactivation was present in blood from 4/42 (9.5%) control females and 11/31 (35%) of those with IP. This frequency of skewed inactivation was seen in both familial and sporadic cases of IP. Analysis of inactivation in mother/daughter pairs, both affected and control subjects, showed no familial consistency of pattern, arguing against specific mutations being associated with particular patterns of inactivation. In the only informative family where both mother and daughter were affected by IP and showed skewed inactivation, the IP mutation was on the active X chromosome. This argues against cell selection during early embryogenesis being the explanation for the skewed inactivation observed. These data confirm that skewed inactivation of one X is observed in lymphocytes from a significant minority of normal females, and is seen with raised frequency in IP heterozygotes. It is not, however, a universally observed phenomenon, and the relationship of X inactivity to the IP mutation appears to be complex. In the case of XLP, though skewed X inactivation patterns are seen in most disease carriers, the frequency with which this phenomenon occurs in normal females renders it an unreliable diagnostic marker for XLP carriers.

Confirmation and further regional assignment of aminoacylase 1 (ACY‐1) on human chromosome 3 using a simplified detection method

An improved method for the detection of aminoacylase‐1 (ACY‐1) is described. Data from human‐rodent interspecific hybrids confirm the assignment of ACY‐1 to human chromosome 3. The most likely site for ACY‐1 appears to be 3p21 to 3pter. The enzyme ACY‐1 hydrolyses both acetyl methionine and acetyl glutamate.

X inactivation patterns in females with Alport's syndrome: a means of selecting against a deleterious gene?

The patterns of X chromosome inactivation in 43 females from families segregating classic Alports syndrome (AS) (X linked hereditary nephritis with deafness) have been analysed. AS carrier females have a most variable clinical course. The aim of the study was to establish whether there was any correlation between the X inactivation pattern of a carrier female and the severity of her disease. No correlation was found in DNA derived from peripheral blood lymphocytes. However, it remains possible that differential patterns of X inactivation may occur in the tissues affected by AS, namely the basement membrane of the kidney, eye, and ear.

Probable assignment of the locus determining human red cell acid phosphatase ACP1 to chromosome 2 using somatic cell hybrids

Twelve independent interspecific hybrid lines, from six different crosses, together with nine subclones, were tested for the presence of the human enzymes ACP1, MOR‐S and ICD‐S. The hybrids were also tested for a total of 27 other human enzymes. With one exception the data were consistent with the synteny of ACP1, MOR‐S and ICD‐S. Detailed chromosome analysis of the subclones confirmed the assignment of these loci to chromosome 2. In the remaining hybrid chromosome 2 was present, together with MOR‐S and ICD‐S but ACP1 was not seen. Possible explanations for this discrepancy are discussed.

45, XO/46, XYq dic mosaicism in a patient with ambiguous genitalia

45, XO/46, XYq dic mosaicism was found in a patient with ambiguous genitalia. The patient had dysgenetic testis and gonadoblastoma.