Preparative dual-beam sorting of the human Y chromosome and in situ hybridization of cloned DNA probes

Bivariate Hoechst/chromomycin flow karyotypes for chromosomes from a Chinese hamster-human hybrid cell line (CH-Y-VII) were established that have retained a human Y chromosome. These bivariate flow karyotypes showed the human Y chromosome to be completely separated from the peaks for the Chinese hamster chromosomes. In preparative dual-beam sorting experiments, 3 X 10(6) chromosomes were sorted from the Y peak into frozen petri dishes. An examination of Q-banded samples of sorted chromosomes revealed that 82% +/- 5% of them were human Y chromosomes. The DNA from the sorted chromosomes (approximately 250 ng) was isolated and used to establish a genomic library (vector lambda gt WES. lambda B). Three clones (YACG 45, 52, 54) of this library containing inserts of repetitive human DNA were used for chromosomal localization by means of in situ hybridization to metaphase spreads of male human lymphocytes and of CH-Y-VII cells. In all three cases, a significant binding to the human Y chromosome was observed. A more detailed study of the chromosomal distribution of sequences homologous to the insert of YACG 45 suggested the existence of minor binding sites on several human autosomes. Southern blot analysis revealed the existence of other human specific sequences without Y chromosome specificity.

Toward a complete linkage map of the human X chromosome: regional assignment of 16 cloned single-copy DNA sequences employing a panel of somatic cell hybrids

Closely linked restriction fragment length polymorphisms (RFLPs) are potentially useful as diagnostic markers of genetic defects, and, in principle, RFLPs can be employed to construct a complete linkage map of the human genome. On the X chromosome, linkage studies are particularly rewarding because in man more than 120 X-linked genes are known. Thus, it is probable that each X-specific RFLP will be of use as a genetic marker of one or several X-linked disorders. To facilitate the search for closely linked RFLPs, we have regionally assigned 16 cloned DNA sequences to various portions of the human X chromosome, employing a large panel of somatic cell hybrids. These probes have been used to correlate genetic and physical distances on Xp, and it can be extrapolated from these data that the number and distribution of available Xq sequences will also suffice to span the long arm of the X chromosome.

Ichthyosis vulgaris with hypogenitalism and hypogonadism: evidence for different genotypes by lipoprotein electrophoresis and steroid sulfatase testing

We report two cases with ichthyosis vulgaris, hypogenitalism and hypogonadism. So far, little endocrinological information has been available on this association and the exact type of ichthyosis was unknown. Our first patient suffered from very severe hypergonadotropic hypogonadism, whereas the second patient showed normal levels of luteinizing hormone, but slightly elevated follicle stimulating hormone values. In lipoprotein electrophoresis we found fast moving beta-lipoproteins in the first patient and a normal electrophoretic mobility of pre- beta and beta-lipoproteins in the second patient. Correspondingly, steroid sulfatase (STS) testing revealed STS deficiency in the first patient and normal STS activity in the second patient, thus excluding X-linked recessive ichthyosis. These two different types in the association of ichthyosis with hypogenitalism and hypogonadism could not be discriminated by clinical, morphological and cytogenetic studies.

Regional localization of the human factor IX gene by molecular hybridization

A cloned cDNA probe encoding human factor IX was used for detecting homologous sequences in rodent human X chromosome hybrids and in human metaphase chromosome preparations. The results of these studies indicate that human factor IX is localized to the Xq27 leads to Xqter region.

On the genetic length of the short arm of the human X chromosome

Published estimates of the length of the human X chromosome are unreliable because they are based on scanty linkage data and complex assumptions about the frequency and distribution of chiasmata in female meiosis. In recent months we have established linkage between restriction fragment length polymorphisms (RFLPs) and several genes on the short arm of the X chromosome. These and previous data can be combined to construct a continuous linkage map spanning the short arm from the Xg gene to the centromere. They suggest that the genetic length of the Xg-Xcen segment may be in the order of 75-90 cM.

Genetic heterogeneity of the ichthyosis, hypogonadism, mental retardation, and epilepsy syndrome. Clinical and biochemical investigations on two patients with Rud syndrome and review of the literature

Major diagnostic criteria for the Rud syndrome are ichthyosis, hypogonadism, mental retardation, and epilepsy. Two unrelated patients are presented and compared with 28 reported cases. Genetical heterogeneity of the Rud syndrome is suggested by differences in clinical features, histological and endocrinological findings, steroid sulfatase activity, and modes of inheritance.

Cloning of genomic sequences from the human Y chromosome after purification by dual beam flow sorting

Human Y chromosomes were purified by dual beam flow sorting from a human X Chinese hamster cell line retaining the Y as the only free human chromosome. DNA was extracted from the Y fraction and cloned into lambda gtWES . lambda B vector arms. More than 100 recombinant clones carrying human inserts have been characterised by Benton-Davis plaque screening and Southern blotting or in situ hybridisation. Several repetitive sequences were found to be predominantly located on the Y, whereas the majority also cross-hybridised with autosomal DNA. One repetitive clone gave a specific hybridisation signal with the X and the Y chromosome but not with autosomes. Preliminary evidence indicates that many clones contain single copy as well as repetitive sequences. However, no Y-specific single copy sequence has yet been identified.

Linkage relationships between Retinoschisis, Xg, and a cloned DNA sequence from the distal short arm of the X chromosome

A cloned DNA sequence, RC8, from the short arm of the X chromosome which is linked to the Duchenne muscular dystrophy (DMD) gene has been employed to study linkage relationships with the Xg-linked retinoschisis (RS) locus. Results of three point linkage analyses in two families suggest that the gene order on Xp is Xg-RS-RC8. Moreover, it can be inferred from these date that the genetic distance between Xg and DMD is approximately 55 cM.

Menkes kinky hair disease: a search for closely linked restriction fragment length polymorphism

In a large kindred with X-linked Menkes disease, linkage studies were performed with a restriction fragment length polymorphism (RFLP) that had been found with a cloned hybridisation probe from the proximal short arm of the X chromosome. This RFLP was considered as a potential genetic marker since the Menkes gene seems to be located near the centromere. Moreover, there is circumstantial evidence that in the (para) centric region of the X chromosome cross-overs are relatively rare. Unexpectedly, however, at least two cross-overs were detected in this family which suggests that the DNA sequence employed is of limited use for early diagnosis and carrier detection in this fatal hereditary disorder.

Linkage studies in a family with X-linked recessive ichthyosis employing a cloned DNA sequence from the distal short arm of the X chromosome

Recently linkage has been described between the Duchenne muscular dystrophy (DMD) gene and a cloned DNA sequence, RC8, that detects restriction fragment length polymorphism and is derived from the distal short arm of the X chromosome. Positive lod scores between RC8 and Xg prompted us to examine the linkage relationship of RC8 to the steroid sulfatase-X-linked recessive ichthyosis (XRI) locus which is situated 15 cM proximal from Xg in the subtelomeric region of Xp. Unexpectedly, at least two crossovers were found among nine informative meioses of an informative family, suggesting that RC8 and XRI may be about 25 cM apart. This implies that the genetic distance between the Xg locus and the DMD locus may exceed 50 cM.

Genetic evidence that a Y-linked gene in man is homologous to a gene on the X chromosome

The mammalian sex chromosomes are thought to be related to each other by sharing a common origin. That is, the X and Y chromosomes originally evolved from a pair of chromosomes that only differed at the locus determining sexual differentiation. For example, this evolutionary relationship is reflected during meiosis in chromosomal pairing between the tip of the human X chromosome short arm and the Y chromosome which presumably implies sequence homology. However, compelling genetic evidence for functional homology between the mammalian X and Y chromosome is lacking. We describe here the localization of a gene to the tip of the short arm of the human X chromosome and evidence for a related gene on the Y chromosome.

An XX male with a single STS gene dose

There is substantial evidence that many XX males arise from an X/Y interchange, so that a terminal Xp segment carrying the Xg locus, but not the neighboring steroid sulfatase (STS) locus, is replaced by part of the Y chromosome. We show here that one of the two X chromosomes of an XX male with low intracellular levels of STS does not express the STS gene.

Adrenal insufficiency, myopathic hypotonia, severe psychomotor retardation, failure to thrive, constipation and bladder ectasia in 2 brothers: adrenomyodystrophy

Two brothers are described who manifested primary adrenal insufficiency, dystrophic myopathy, severe psychomotor retardation, failure to thrive, fatty degeneration of the liver, megalocornea, chronic constipation, and terminal bladder ectasia until their death at 3 8/12 and 1 7/12 years, respectively. The differential diagnosis to similar syndromes is discussed. This combination of problems apparently has not yet been described. The term adrenomyodystrophy is suggested.

Adrenoleukodystrophy: diagnosis and carrier detection by determination of long-chain fatty acids in cultured fibroblasts

In cultured fibroblasts of adrenoleukodystrophy (ALD) patients and most heterozygotes, concentrations of long-chain fatty acids (greater than C22) were significantly higher than in controls when cells were assayed 4-5 days after reaching confluence. Intermediate values were found in three independent cultures of a girl with manifest ALD, suggesting that a significant proportion of her fibroblasts does not express the defect. Though long-chain fatty acid concentrations in heterozygotes were somewhat higher than expected, suggesting a slight preponderance of defective cells, it may be too early to conclude that somatic selection is a consistent finding in cultured fibroblasts of ALD carriers.

Flow cytometric characterization of a Chinese hamster X man hybrid cell line retaining the human Y chromosome

A Chinese hamster X man hybrid cell line (CH-Y-VII) was established which retains a free human Y chromosome. Exponentially growing CH-Y-VII cells were arrested with colcemid; metaphase chromosomes were isolated and stained with 33258 Hoechst (HO) plus Chromomycin A3 (CA3), or with ethidium bromide (EB). The HO/CA3-stained chromosomes were measured in a dual beam flow cytometer, and bivariate HO/CA3 flow karyotypes and univariate HO and CA3 flow karyotypes were established. EB-stained chromosomes were analyzed in a modified Becton Dickinson FACS-Sorter. For all three stains used, the human Y chromosome forms a separate peak in univariate flow karyotypes; the optimum resolution was obtained for the HO distribution. In the bivariate HO/CA3 flow karyotype, the peak for the human Y chromosome is completely separated from the Chinese hamster chromosomes.

Agenesis of corpus callosum, ocular, and skeletal anomalies (X-linked dominant Aicardi's syndrome) in a girl with balanced X/3 translocation

Aicardi's syndrome, which is characterized by agenesis of the corpus callosum, specific chorioretinal abnormalities, and defects of vertebrae and ribs, is considered a probable X-linked dominant trait with male lethality. All features of this syndrome were seen in a girl with a de novo balanced X/3 translocation (46,X,t(X;3)(p22;q12)). It is hypothesized that the clinical picture is the consequence of chromosome breakage within the Aicardi locus. Then, unusual X-inactivation patterns in blood and fibroblasts of this patient can be explained by somatic selection against cells with the Aicardi phenotype.

X-linked recessive ichthyosis in three sisters: evidence for homozygosity

A family with ichthyosis, severely affecting both men and women, is reported. The clinical, histological and genetic data are strongly suggestive of X-linked recessive ichthyosis. Assay of steroid sulphatase in cultured skin fibroblasts from two ichthyotic female patients revealed an absence of this enzyme and thus confirmed this diagnosis. To our knowledge, this is the first report of proven X-linked recessive ichthyosis in women.

Activity of steroid sulfatase in fibroblasts with numerical and structural X chromosome aberrations

In cultured fibroblasts of patients with numerical and structural X chromosome aberrations the activity of steroid sulfatase (STS) is correlated with the number of functional STS gene copies. While normally, this X-linked gene is not inactivated, our data suggest that it may be subject to inactivation when carried on a structurally altered X-chromosome. Similar inactivation patterns have been reported earlier for the Xg locus which, like STS, is located on the distal portion of Xp.

[Propionic acidemia associated with hypertrophic pyloric stenosis and bouts of severe hyperglycemia (author's transl)]

A newborn is presented with hyperexcitability, drowsiness and later-on with frequent vomiting and muscular hypotonia. Examination of the urine by gas chromatography-mass spectrometry lead to the diagnosis of propionic acidemia which was confirmed enzymatically in fibroblasts. Two unusual features were encountered in this case: There were severe bouts of hyperglycemia with blood glucose values up to 396 and 747 mg/100 ml; furthermore x-ray studies and autopsy revealed a hypertrophic pyloric stenosis.

Addison disease and cerebral sclerosis in an apparently heterozygous girl: evidence for inactivation of the adrenoleukodystrophy locus

Cerebral sclerosis and Addison disease were observed at age 14 years in a previously healthy sister of an affected boy. Clinical findings and family history established the diagnosis of X-linked adrenoleukodystrophy, which is normallly confined to males. The affected female has a normal karyotype; both X chromosomes are morphologically inconspicuous. Thus, this patient may be the first documented example of clinically manifest adrenoleukodystrophy in a heterozygote, which supports our previous conclusion that this X-linked locus is subject to inactivation.

Regional assignment of the gene locus for steroid sulfatase

The gene locus for steroid sulfatase, deficiency of which causes X-linked ichthyosis, is assigned to Xp11 leads to Xpter by analysis of 24 man-Chinese hamster somatic cell hybrids. High steroid sulfatase activity in a hybrid clone having retained only part of Xq is explained by demonstration of an additional late-replicating human X chromosome. This observation confirms previous evidence for noninactivation of the STS locus.

X-linked steroid sulfatase: evidence for different gene-dosage in males and females

Steroid sulfatase (STS) activities in female fibroblast strains are significantly higher than in male strains, as determined by cleavage of dehydroepiandrosterone sulfate. The difference is probably not due to hormonal control of gene expression, but suggests that for this X-linked locus there is no gene dosage compensation.

Assignment by deletion mapping of the steroid sulfatase X-linked ichthyosis locus to Xp223

A male child and his mother who are nullisomic and monosomic, respectively, for the distal portion of Xp because of an unbalanced X-Y translocation were tested for steroid sulfatase activity after clinical examination had yielded evidence for ichthyosis in the boy. Deficiency of steroid sulfatase was found in the male patient, while in his mother enzyme levels were in the heterozygous range. These results, based on cytogenetic evidence obtained with an elongation technique, indicate that the STS locus is at Xp 223.

The presence of androgen-binding receptors in genital and nongenital skin fibroblasts

The specific, receptor-dependent 5 alpha-dihydrotestosterone-binding capacity of cultured fibroblasts derived from genital and nongenital skin has been compared. With the methods employed, the detectable amount of the DHT receptor in nongenital skin-derived fibroblasts is variable, often approaching the limit of detectability. Therefore it is concluded that for differential diagnosis of disorders of sexual development, DHT-binding studies should be performed with genital skin fibroblasts only.

Progressive myoclonus epilepsy. A variant with probable X-linked inheritance

The syndrome of myoclonus, epilepsy, and mental deficiency is observed in a number of distinct nosologic entities differing with respect to clinical course, (--) pathologic, and biochemical findings. Genetically, the heterogeneity within this group of disorders is shown by the occurrence of autosomal recessive and dominant forms with incomplete penetrance. In this paper we report on a sibship with at least four affected males suffering from progressive myoclonus epilepsy, ataxia, and mental deterioration. The syndrome is probably X-linked, as suggested by the maternal transmission and mild, variable symptoms in some female carriers. In a survey of the literature we have found another pedigree suggesting X-linked inheritance of this variant of progressive myoclonus epilepsy.

Periodic hypokalemic paralysis transmitted by an unaffected male with negative family history: a delayed mutation?

A pedigree is described that includes three cases of periodic hypokalemic paralysis. Apparently, the disease has arisen by de novo mutation in a father of two affected daughters, who, however, is not affected himself. This is unexpected, since in males the disorder is generally inherited as a fully dominant trait. Therefore we propose that these findings result from an early somatic or a half-chromatid mutation.

Clinical and biochemical investigations on patients with partial deficiency of placental steroid sulfatase

We report on three independent cases with a partial deficiency of placental steroid sulfatase (E.C.3.1.6.2). Upon routine pregnancy monitoring these patients were detected on the basis of low estriol excretion and failing induction of labor. In all three cases a male was delivered and subsequently the diagnosis of partial deficiency of placental steroid sulfatase was confirmed enzymatically in placenta homogenates. In one case, fibroblast cultures were established from skin explants of mother and son. In fibroblasts of the child, as in placental tissue, the activity of steroid sulfatase was only 34% of normal. Similar values were obtained for arylsulfatase C, though this enzyme is clearly separable from steroid sulfatase by electrophoresis. In cells of the mother, enzyme activities were unremarkable.

Preferential X inactivation in human placenta membranes: is the paternal X inactive in early embryonic development of female mammals?

In placenta membranes of newborn girls carrying electrophoretically distinguishable G6PD alleles, the maternally derived isozyme is expressed preferentially. This phenomenon cannot be explained by allelic differences in enzyme activity or by somatic selection directed against cells with particular G6PD phenotypes. Instead, it may be that in this tissue X inactivation is nonrandom. Preferential expression of the maternal X chromosome, as has been shown in marsupials and in extraembryonic membranes of rodents and now in man, may reflect the state of activity of the X chromosomes in the early stages of female embryonic development.

Distribution of G6PD phenotypes in red blood cells of Southern African Negroids: evidence for somatic selection

In a recent population study, we observed a striking deficit of G6PD heterozygotes among Southern African Negroid females. This finding was interpreted tentatively as evidence for a small number of hematopoetic stem cells in man. In a follow-up study we examined peripheral blood and cord blood in 547 mothers and in their newborn offspring. In mothers and sons, the frequencies of the G6PD alleles are apparently quite different. When the allele frequencies determined in sons are used for calculation of the expected phenotype frequencies in mothers and daughters, there is a large deficit of maternal G6PD AB phenotypes, and an equivalent surplus of G6PD homozygotes. However, no relevant heterozygote deficit is observed in newborn daughters. This discrepancy may be explained by the assumption that in peripheral blood of heterozygotes carrying the GdA- allele, G6PD-deficient cells progressively become eliminated during development from birth to adulthood. In other words, the large heterozygote deficit observed in adult females may be due to somatic selection rather than to a small pool of hematopoetic cells at the time of X differentiation.

On the incidence of unilateral and bilateral colour blindness in heterozygous females

In 303 mothers of colour-blind sons, both eyes were tested with pseudoisochromatic plates and with the anomaloscope. Two hundred thirty healthy normal and 56 colour-blind males served as controls. In good agreement with the expected proportion of homozygotes in our sample, 17 colour-blind mothers were detected. Eight others had difficulty reading pseudoisochromatic plates and were conspicuous at the anomaloscope. In these, both eyes were affected to a very similar, moderate degree. Monocular disturbances of colour vision were not observed in the entire series. Our data suggest that (1) in most (if not all) of the carriers with colour vision impairment, there is no complete lack of normal retina cones, and (2) the proportion of defective retina cones is remarkably similar in both eyes of individual heterozygotes. The latter observation may indicate that at the time of X-differentiation there is a common primordial cell pool for both retinas.

X-linked mental retardation: transmission of the trait by an apparently unaffected male

A pedigree is presented in which an apparently unaffected man transmitted the gene for X-linked mental retardation to at least four of his 12 daughters. None of his 12 sons was mentally retarded. These findings may be explained by a somatic mutation and germinal mosaicism in the father or by a half chromatid mutation in maternal gametes.

Evidence for preferential X-chromosome inactivation in a family with Fabry disease

Severe clinical signs of Fabry disease were observed in four of eight heterozygous daughters of a male patient. Activities of alpha-galactosidase A in serum, white blood cells, and hair roots of the manifesting carriers were markedly lower than 50% of normal. These findings are not easy to interpret in terms of random X inactivation alone; several alternative models including nonrandom (preferential) X inactivation are discussed.

Tentative evidence for 3--4 haematopoetic stem cells in man

Blood specimens from a random sample of 981 South African Negroid females were typed electrophoretically inter alia for their G-6-PD phenotypes, The allele frequency for GdB and GdnonB was found to be 0.8126 and 0.1874 respectively. Calculating the number of individuals expected for each phenotypic class, a highly significant deviation from the Hardy-Weinberg equilibrium became manifest, i.e. there was a deficit of 24.6% of heterozygotes and an excess of 12.3% of each of the two classes of homozygotes. Several possible reasons for this discrepancy e.g. the effects of pooling sub-samples, selection and misclassifications due to insufficient staining were examined and were found not be likely explanations for the observed phenomenon. Instead, the result is interpreted as due to only 3--4 stem cells which give rise to the haematopoetic system in man.

Adrenoleukodystrophy (Siemerling-creutzfeldt disease): Heterozygote with two clonal fibroblast populations

On the fifth day after subcultivation,, fibroblasts of two unrelated patients with adrenoleukodystrophy (Siemerling-Creutzfeldt disease (SCD)) developed typical morphologic anomalies which could be seen by light microscopy. From skin biopsy material of an obligatorily heterozygous womam, both normal and morphologically defective colonies could be isolated. These findings suggest that the morphologic alterations are an expression of the defect in Siemerling-Creutzfeldt disease. Futhermore, they suggest that the SCD locus is subject to lyonization.

Fabry's disease: heterozygote detection by hair root analysis

Fabry's disease (angiokeratoma corporis diffusum) can be diagnosed by determination of alpha-galactosidase activity in single hair roots. A technique has been developed permitting subsequent analysis of enzyme activity and protein content of hair root cells. We have applied this method examining 8 obligatorily heterozygous sisters as well as their 5 daughters and 10 sons. Especially for identification of heterozygotes, the method described proved to be easy and reliable.

Prenatal diagnosis of homoxygous familial hypercholesterolemia: investigation of a case at risk

Cultivated amnion cells obtained from a pregnancy at risk for the homozygous form of familial hypercholesterolemia were analyzed, as were fibroblasts from normal, heterozygous and homozygous controls. Three different methods were employed in order to compare their diagnostic value: i. Acetate incorporation into the cellular 3beta-OH-sterol fraction; ii. LDL-binding to the cell surface receptor; and iii. Oleate incorporation into the cholesterylester pool of the cells after addition of LDL to lipoprotein-deficient growth medium. The best discrimination between normal, heterozygous and homozygous cells was achieved using the third technique. On the basis of the acetate incorporation analysis, we concluded that the child is not homozygous, but probably completely unaffected. This diagnosis was confirmed by repeated determinations of plasma cholesterol levels during the first 11 months of life. Our investigations further substantiate the specularion that prenatal diagnosis of this disorder is possible.

Leukodystrophy, skin hyperpigmentation, and adrenal atrophy: Siemerling-Creutzfeldt disease. Transmission through several generations in two families

Two apparently unrelated families with a history of leukodystrophy associated with adrenal insufficiency are presented. Only about 20 cases of this syndrome have been reported until now. It was first described by Siemerling and Creutzfeldt; therefore we propose the designation Siemerling-Creutzfeldt disease. Our pedigrees include 15 additional cases and prove that this disease is inherited as an X-linked or as an autosomal dominant trait with male sex limitation. Within these families, the interindividual variability of clinical signs is remarkable. Patients can survive into the fifth decade, and one has reproduced. Attempts to identify heterozygotes on the basis of endocrinologic investigations were unsuccessful.