Lateral asymmetry of constitutive heterochromatin in human chromosomes

Summary Variations in lateral asymmetry of constitutive heterochromatin were studied in 30 normal individuals with reference to the chromosomal regions 1q12, 9q12, 15p11, 16q12 and Yq12. The technique consisted of growing human lymphocytes for one cell cycle in BrdU, staining with 33258 Hoechst, exposing them to UV light, treating them with 2 x SSC, and staining with Giemsa. This procedure revealed asymmetric staining in the region of constitutive heterochromatin in these chromosomal regions. Chromosomes 15, 16, and Y showed simple lateral asymmetry, whereas chromosome 1 showed both simple and compound asymmetry. In 15 cases, compound lateral asymmetry was evident in both homologues of chromosome 1, 12 cases showed compound lateral asymmetry in one homologue and simple lateral asymmetry in the other, and the remaining three cases showed simple lateral asymmetry in both the homologues. The centromere region of chromosome 9 stained symmetrically with this technique. The lateral asymmetry is presumed to reflect the strand bias in the distribution of thymine in satellite DNA fractions.     

A new type of inversion of a human Y chromosome.

Using chromosome banding techniques, a phenotypically normal male was found to have an abnormal banding pattern of the Y chromosome. By the constitutive heterochromatin staining method, a darkly stained band was located on the short arm and the proximal region of the long arm. The quinacrine staining method also showed a similar abnormal banding pattern: a brightly fluorescing band was seen on the short arm and the proximal region of the long arm. By the conventional Giemsa staining method, however, no specific morphological abnormality was detected in the aberrant Y. On detailed karyotype analyses no recognizable abnormality of banding patterns of any other chromosome was found aside from the abnormal Y. The abnormality was determined to be a complex inversion of the Y chromosome, which is described as 46,X,inv(Y)(pter leads to p11::q11 leads to q12::cen::q12 leads to qter).     

Isolabeling of the long arm of the human Y chromosome demonstrated by the FPG technique

Isolabeling segments were found in the distal region of the long arm of Y chromosomes derived from human leukocytes grown through two replication cycles in medium containing BrdU and stained by the FPG technique. Three main types of Y chromosome staining patterns were demonstrated: I-Y chromosome with typical SCD, II-Y chromosome with weakly stained distal regions of long arms (isolabeling segments), III-Y chromosome with both terminal regions displaying SCD interrupted by one isolabeled segment. The existence of different types of Y chromosome staining patterns was explained on the basis of the previously described hypothesis of unequal distribution of thymine residues between two DNA polynucleotide chains in the distal part of the long arms of human Y chromosomes.     

A new type of inversion of a human Y chromosome

Summary Using chromosome banding techniques, a phenotypically normal male was found to have an abnormal banding pattern of the Y chromosome. By the constitutive heterochromatin staining method, a darkly stained band was located on the short arm and the proximal region of the long arm. The quinacrine staining method also showed a similar abnormal banding pattern: a brightly fluorescing band was seen on the short arm and the proximal region of the long arm. By the conventional Giemsa staining method, however, no specific morphological abnormality was detected in the aberrant Y. On detailed karyotype analyses no recognizable abnormality of banding patterns of any other chromosome was found aside from the abnormal Y. The abnormality was determined to be a complex inversion of the Y chromosome, which is described as 46,X,inv(Y)(pterp11::q11q12::cen::q12qter).     

Structural organization of the heterochromatic region of human chromosome 9

Giemsa-11, G-banding and Lateral Asymmetry staining techniques were used to define the substructure of the C-band heterochromatin of human chromosome 9, in a sample of 108 different chromosomes 9, from 54 individuals. In this sample, the juxtacentromeric portion of the C-band region stained positive by the G-banding technique while Giemsa-11 delineated a more distally located block. Examination of the pericentric inversions generally revealed that the entire C-band region is changed with the substructural organization left intact; i.e. the G-band is proximal, the G-11 distal to the centromere. The partial pericentric inversions were found to have larger than average amounts of G-band heterochromatin on the short arm. The G-11 staining was in its usual position on the long arm with none on the short arm. Such apparent inversions therefore may not represent true inversions. — Long heterochromatic regions frequently had a segmented appearance when stained with G-11; there was a dark G-band within the pale heterochromatic region when stained with the G-banding technique which corresponded in location to the achromatic gap produced by G-11. This extra G-band may have been derived from the juxtacentromeric G-band by processes analogous to unequal crossing over. — Simple lateral asymmetry was consistently present only in the G-band heterochromatin of those chromosomes 9 containing large blocks of G-band positive material. Examination of the portion of the C-band which would correspond to the G-11 positive material revealed no consistent patterns of asymmetry. Usually both strands were heavily stained and symmetrical but occasionally there were light areas present on one strand suggestive of compound lateral asymmetry.     

A refined physical map of the long arm of human chromosome 16

Mapping of 33 anonymous DNA probes and 12 genes to the long arm of chromosome 16 was achieved by the use of 14 mouse/human hybrid cell lines and the fragile site FRA16B. Two of the hybrid cell lines contained overlapping interstitial deletions in bands q21 and q22.1. The localization of the 12 genes has been refined. The breakpoints present in the hybrids, in conjunction with the fragile site, can potentially divide the long arm of chromosome 16 into 16 regions. However, this was reduced to 14 regions because in two instances there were no probes or genes that mapped between pairs of breakpoints.     

Nonfluorescent Y chromosomes. Cytologic evidence of origin

Summary Twelve presumptive structurally altered Y chromosomes were studied with Q-, G-, G-11, C-, Cd, and lateral asymmetric banding techniques and were compared with normal X and Y chromosmes and with an abnormal [i(Yq)] Y chromosome that exhibited intact fluorescence. Significant to this work is the fact that the Y chromosome has a small block of Giemsa-11 heterochromatin adjacent to the centromere on the long arm, while the X chromosome does not, which allows a distinction between the X-and Y-derived chromosomes. Two of the twelve altered chromosomes of either X or Y origin are small nonfluorescent rings. Each ring has a G-11-positive band of heterochromatin at the centromere, confirming Y origin. Each of the normal-length nonfluorescent presumed Ys and a Y with a fluorescent band in the center have one G-11 band at the centromere and another at an equal distance from the end of the long arm, the bands also being Cd positive, indicating that these chromosomes are pseudodicentric. The likely mechanism of origin is a break at the distal bright heterochromatin/ euchromatin junction (or within the bright segment in the chromosome with the bright center band), fusion of the sister chromatids at the breakpoints, and loss of the distal segment.     

Localization of the proto-oncogene MOS to 8q11-q12 by in situ chromosomal hybridization

The human MOS proto-oncogene has been mapped previously to two different sites on chromosome 8 (8q22 and 8q11). Here we report in situ hybridization data from two different laboratories which confirm the localization of MOS to the proximal region of the long arm of chromosome 8, at 8q11-q12.     

Localization of HeLa cell tumor-suppressor gene to the long arm of chromosome II.

Cytogenetic and molecular genetic analyses of human intraspecific HeLa x fibroblast hybrids have provided evidence for the presence of a tumor-suppressor gene(s) on chromosome 11 of normal cells. In the present study, we have carried out extensive RFLP analysis of various nontumorigenic and tumorigenic hybrids with at least 50 different chromosome 11-specific probes to determine the precise location of this tumor-suppressor gene(s). Two different hybrid systems, (1) microcell hybrids derived by the transfer of a normal chromosome 11 into a tumorigenic HeLa-derived hybrid cell and (2) somatic cell hybrids derived by the fusion of the HeLa (D98OR) cells to a retinoblastoma (Y79) cell line, were particularly informative. The analysis showed that all but one of the nontumorigenic hybrid cell lines contained a complete copy of the normal chromosome 11. This variant hybrid contained a segment of the long arm but had lost the entire short arm of the chromosome. The tumorigenic microcell and somatic cell hybrids had retained the short arm of the chromosome but had lost at least the q13-23 region of the chromosome. Thus, these results showed a perfect correlation between the presence of the long arm of chromosome 11 and the suppression of the tumorigenic phenotype. We conclude therefore that the gene(s) involved in the suppression of the HeLa cell tumors is localized to the long arm (q arm) of chromosome 11.     

一例t（Y;15）并t（14;21）复合易位的细胞与分子遗传学研究

本文对一便生育过先天愚型儿的个体刊进行了细胞与分子遗传学研究。发现先证者拥有ｔ（１４;２１）用一个短臂增大变异为１５号标记染色体。通过Ｇ－显带、Ｃ－显带、Ｑ－显带、硝酸银染色及Ｙ染色体长臂异染色质区特异控针ｐＹ３．４对先证者基因组ＤＮＡ的斑点杂交和中期染色体的原位杂交,证实变异部分由Ｙ染色体长臂异染色质区易位所形成,从而排除了巨大随体的存在或其他染色体参与重排形成变的可能性,结果表明,常规显带与染     

Lateral asymmetry in human constitutive heterochromatin

Human lymphocytes were grown for one replication cycle in BrdU, stained with 33258 Hoechst, exposed to UV light and subsequently treated with 2 x SSC and stained with Giemsa. This technique differentially stains the constitutive heterochromatin of chromosomes 1, 9, 15, 16, and the Y. In the heterochromatin of chromosome 9 both sister chromatids stained darkly and symmetrically but in the other four chromosomes the heterochromatin showed lateral asymmetry, one chromatid being darkly stained while its sister chromatid was as pale or paler than the rest of the chromosome. The lateral asymmetry is presumed to reflect an underlying asymmetry in distribution of thymine between the two strands of the DNA duplex in the satellite DNA component of the chromosomes. In some number 1 chromosomes compound lateral asymmetry was seen; darkly staining material was present on both sister chromatids although at any given point lateral asymmetry was maintained so that if one chromatid stained darkly the corresponding point on the sister chromatid was very pale. The pattern of compound lateral asymmetry varied among the number 1 chromosomes studied but was constant for any one homologue from one individual. This technique reveals a previously unsuspected type of polymorphism within the constitutive heterochromatin of man.     

Extensive DNA sequence homologies between the human Y and the long arm of the X chromosome.

It has been proposed that sequence homology should exist between the short arms of the human sex chromosomes, in the regions pairing at meiosis. Out of 40 clones picked at random from a collection of non-repetitive DNA sequences derived from the human Y chromosome, we have found nine sequences which show very high homology with sequences located on the X chromosome. All nine probes originate from the euchromatic part of the Y chromosome. All the homologous sequences are located within the Xq12-Xq22-24 region. None of them map to the short arm of the X chromosome. We conclude that an important part of the euchromatic region of the Y chromosome is homologous to the middle of the X chromosome long arm, possibly as a result of recent translation event(s).     

Human homologs of two testes-expressed loci on mouse chromosome 17 map to opposite arms of chromosome 6

Our laboratory has recently cloned and characterized two testes-expressed loci--the Tcp-10 gene family cluster and the D17Si11 gene--that map to the proximal portion of mouse chromosome 17. Human homologs of both loci have been identified and cloned. Somatic cell hybrid lines have been used to map the human homolog of D17Si11 to the short arm of chromosome 6 (p11-p21.1) along with homologs of other genes from the (Pim-1)-(Pgk-2) region of the mouse chromosome. The human TCP 10 locus maps to the long arm of chromosome 6 (q21-qter) along with homologs of other genes from the mouse chromosome 17 region between the centromere and Pim-1. The mapping of large portions of the mouse t haplotype to unlinked regions on human chromosome 6 rules out the possibility that a t-haplotype-like chromosome could exist in humans.     

Physical mapping of unique nucleotide sequences on identified rice chromosomes

A physical mapping method for unique nucleotide sequences on specific chromosomal regions was developed combining objective chromosome identification and highly sensitive fluorescence in situ hybridisation (FISH). Four unique nucleotide sequences cloned from rice genomic DNAs, varying in size from 1.3 to 400 kb, were mapped on a rice chromosome map. A yeast artificial chromosome (YAC) clone with a 399 kb insert of rice genomic DNA was localised at the distal end of the long arm of rice chromosome (1q2.1) and a bacterial artificial chromosome (BAC) clone (180 kb) containing the rice leaf blast-resistant gene (Pi-b) was shown to occur at the distal end of the long arm of chromosome 2 (2q2.1). A cosmid (35 kb) with the resistance gene (Xa-21) against bacterial leaf blight was mapped on the interstitial region of the long arm on chromosome 11 (11q1.3). Furthermore a single RFLP marker, 1.29 kb in size, was mapped successfully to the distal region of the long arm of rice chromosome 4 (4q2.1). For precise localisation of the nucleotide sequences within the chromosome region, image analyses were effective. The BAC clone was localised to the specific region, 2q2.1:96.16, by image analysis. The result was compared with the known location of the BAC clone on the genetic map and the consistency was confirmed. The effectiveness and reliability in physically mapping nucleotide sequences on small plant chromosomes achieved by the FISH method using a variety of probes was unequivocally demonstrated.     

A deletion map of the human Yq11 region: implications for the evolution of the Y chromosome and tentative mapping of a locus involved in spermatogenesis.

A deletion map of Yq11 has been constructed by analyzing 23 individuals bearing structural abnormalities (isochromosomes, terminal deletions and X;Y, Y;X, or A;Y translocations) in the long arm of the Y chromosome. Twenty-two Yq-specific loci were detected using 14 DNA probes, ordered in 11 deletion intervals, and correlated with the cytogenetic map of the chromosome. The breakpoints of seven translocations involving Xp22 and Yq11 were mapped. The results obtained from at least five translocations suggest that these abnormal chromosomes may result from aberrant interchanges between X-Y homologous regions. The use of probes detecting Yq11 and Xp22.3 homologous sequences allowed us to compare the order of loci within these two chromosomal regions. The data suggest that at least three physically and temporary distinct rearrangements (pericentric inversion of pseudoautosomal sequences and/or X-Y transpositions and duplications) have occurred during evolution and account for the present organization of this region of the human Y chromosome. The correlation between the patient' phenotypes and the extent of their Yq11 deletions permits the tentative assignment of a locus involved in human spermatogenesis to a specific interval within Yq11.23.     

Cytochemical heterogeneity of the C-band in human chromosome 1

Summary The heterogeneity of the C-band of human chromosome 1 has been evaluated using several selective staining methods: C-banding (CBG), distamycin A plus 4-6-diamidino-2-phenylindole (DA/DAPI) and Giemsa G-11 pattern following the treatment with the restriction endonucleases AluI and HaeIII. The bands produced by each method are characteristic but not identical. The total C-band is resistant to AluI treatment. The bands induced by HaeIII and the one stained by DA/DAPI are markedly similar but smaller than the C-band. The G-11 technique stains yet smaller regions than those of HaeIII and DA/DAPI. Depending on the expression of staining properties, the C-band of chromosome 1 usually consists of three subdivisions: the proximal, intermediate and distal regions, suggesting an extremely heterogeneous nature. The staining variations between different regions are further substantiated by studies of a reciprocal translocation where the proximal region and the remaining C-band of chromosome 1 are separate.     

Chondrodysplasia punctata with X;Y translocation

Summary We have studied a family in which the mother and her son were carriers of an X;Y translocation, der(X)t(X;Y) (p22.3;q11). The mother was of slightly short stature and had mildly short upper extremities. The son had epiphyseal punctate calcifications, mildly short extremities, a flattened nasal bridge, and mental retardation (chondrodysplasia punctata). The extra bands on the short arm of the X chromosome were identified as deriving from the long arm of the Y chromosome, using in situ hybridization with a Y-chromosome-specific DNA probe (pHY10). The chondrodysplasia punctata seen in our case may be associated with the abnormality of the distal short arm of the X chromosome caused by X;Y translocation.     

Linkage of the evolutionarily-related serum albumin and alpha-fetoprotein genes within q11-22 of human chromosome 4

Albumin and alpha-fetoprotein are structurally related serum proteins, having a similar gene structure and, conceivably, a common evolutionary origin. To test their relative arrangement in the human genome, the serum albumin and alpha-fetoprotein genes were mapped by in situ hybridization of cloned human albumin or alpha-fetoprotein cDNA to human mitotic chromosome preparations. Analysis of cells hybridized with the serum albumin probe showed that 39% of cells exhibited grains on the proximal portion of the long arm of chromosome 4 (bands q11-22), with these grains comprising 30% of all labeled sites throughout these mitoses. Similarly, in cells hybridized with the alpha-fetoprotein probe, 39% of cells were observed to contain silver grains on 4q11-22, these grains constituting 20% of all labeled sites in these cells. These results demonstrate chromosomal localization and linkage of the serum albumin and alpha-fetoprotein genes within bands q11-22 of the long arm of human chromosome 4.     

BrdU-Hoechst-Giemsa analysis of DNA replication in synchronized lymphocyte cultures

The combination of a technique of reversible methotrexate (MTX) imposed G₁/S block in cultures of human lymphocytes with the BrdU-Hoechst-Giemsa technique permitted the study of DNA replication patterns in individual chromosomes at different intervals of the S phase in a cell cohort with uniform S + G₂ duration. The procedure did not increase either the frequency of chromosomal breakage or SCE freqeuncy. The technique applied permitted visualization of the banding pattern in over 90% of mitoses. Examination of mitoses following different times of exposure to BrdU revealed a high degree of synchrony in the progression of the cell cohort examined through the S phase.The presence of two distinct late replication patterns of the allocyclic X chromosome was confirmed in studies on lymphocytes from normal human females by this technique. Interindividual and intercellular differences of the replication pattern have been demonstrated. The replicating patterns from one individual were relatively constant.The analysis of the Y chromosome has revealed marked differences of the termination of replication in individual cells. Euchromatic regions have been shown to complete DNA synthesis first, followed by the distal part of the long arm and, finally, by the region of Yq11/Yq12 junction. Lateral asymmetry was localised at this region.This paper was presented as a preliminary communication at the Helsinki Chromosome Conference Aug. 29–31, 1977, and, in its final form, at the 7th International Chromosome Conference, Oxford, Aug. 26–30, 1980.     

Azoospermia and cryptorchidism in a male with a de novo reciprocal t(Y;16) translocation

An apparently balanced reciprocal translocation between the long arm of the Y chromosome and the long arm of the chromosome 16 t(Y;16)(q12;q13) is described in an infertile man with azoospermia and cryptorchidism. The patient was phenotypically normal and had bilateral inguinal hernia repair with orchidopexy at the age of 8 years. Histological examination of testicular biopsies revealed maturation arrest. Y/autosome translocations in the literature are relatively rare and mostly associated with infertility. To our knowledge, this is the sixth report about the reciprocal t(Y;16) translocation in the literature but the first presenting with cryptorchidism.