A human X-Y homologous region encodes "amelogenin"

Deletion mapping of H-Y antigen to the long arm of the human Y chromosome

A gene encoding or controlling the expression of the H-Y transplantation antigen was previously mapped to the human Y chromosome. We now report the sublocalization of this gene on the long arm of the human Y chromosome. Eight patients with Y-chromosomal abnormalities were examined with a series of existing and new DNA markers for the Y chromosome. The resulting deletion map was correlated with H-Y antigen expression. We conclude that the H-Y antigen gene maps to a portion of deletion interval 6 that is identified by specific DNA markers.

Human ameloblastoma tumors express the amelogenin gene

Instructive signals are responsible for the regulation of the expression of gene products characteristic of many cell lineages during normal development and potentially during neoplasia. The odontogenic origin of ameloblastomas is based largely on the similarity in histologic appearance between the tumor and the developing tooth organ. A pathognomonic pattern for odontogenic tissue-specific gene expression in ameloblastomas has not been previously shown. In these studies, the gene expression parameters for human ameloblastomas have been characterized with the techniques of messenger RNA phenotyping in combination with Northern and in situ hybridization analysis of messenger RNA. The results of these studies confirm that amelogenin, a gene transcribed solely by differentiated ameloblasts, was expressed by epithelial cells from human ameloblastomas. This observation suggests that the instructive signals required for ameloblast differentiation are shared during normal development and tumorigenesis of odontogenic epithelium.

The Y chromosome as a tool for studying human evolution

The use of the Y chromosome in human evolutionary research has only recently begun to gain momentum, partly because of a paucity of polymorphism. Differences in male/female behaviour patterns and the unique mode of inheritance of the Y chromosome also complicate interpretation of the data on Y chromosome variation.

Mapping and expression of the ubiquitin-activating enzyme E1 (Ube1) gene in the mouse

The nucleotide sequence of the human cDNA encoding ubiquitin-activating enzyme E1 is more than 99% identical with the human A1S9T cDNA, a gene that has been shown to complement the temperature-sensitive mutant mouse cell line, tsA1S9. The amino acid sequences of the proteins encoded by these two cDNA sequences are identical, and both cDNAs were previously shown to be located in the same region of the human X chromosome; thus, ubiquitin-activating enzyme E1 and A1S9T appear to be the same gene, designated UBE1. By in situ hybridization to metaphase chromosomes from male mice and by Southern blot analysis of male and female mouse DNA, we show that, in the mouse, a human UBE1 cDNA probe identified both X- and Y-linked loci. Ube1 is located at band A2 of the mouse X Chromosome (Chr) and Ube2 on the short arm of the Y Chr. This is in contrast to the situation in the human, where there is no evidence for Y-linked sequences related to UBE1. Mapping of the Ube1 gene in interspecific backcrosses between Mus spretus and C57BL/6 shows that the Ube1 locus maps close to Timp, in a conserved region of the mouse and human X Chrs that include Otc, Cybb, Syn1, Timp, and Araf. Expression of Ube1 on the inactive X Chr was examined to determine whether this gene is subject to X-Chr inactivation in the mouse, as there is previous evidence that the human UBE1 gene escapes, at least partially, X inactivation. Sequencing of reverse transcriptase polymerase chain reaction (RT-PCR) products from M. spretus, C57BL/6J, and T(X;16)16H x M. spretus F1 female mice indicates that the mouse Ube1 gene is subject to X-Chr inactivation in vivo. This represents a new example of differences between the sex chromosomes of mouse and human.

Sex determination of forensic samples by dual PCR amplification of an X-Y homologous gene

Sex determination by polymerase chain reaction (PCR) analysis of the X-Y homologous amelogenin gene is highly reliable since the detection of an X-specific amplified fragment validates the procedure. Previously, we reported that 250 ng of template DNA are required for sex determination by this method. We report here a refinement of the technique to include dual PCR. Dual PCR using two sets of primers results in the detection of X- and Y-specific amplified fragments from as little as 0.005 ng of template DNA. This is a powerful technique for the analysis of trace forensic samples and its application is discussed.

Capture PCR: efficient amplification of DNA fragments adjacent to a known sequence in human and YAC DNA

We have devised a procedure, termed capture PCR (CPCR), that permits the rapid isolation of DNA segments situated adjacent to a characterized nucleotide sequence. In this procedure, a DNA sample is restriction-digested and a linker, comprising two base-paired oligonucleotides, is added to the ends by ligation. Multiple extension reactions are performed using a biotinylated primer derived from the known sequence, permitting the subsequent isolation of extension products on a streptavidin-coated support. The enriched fragments are amplified exponentially using another specific oligonucleotide, hybridizing 3' to the biotinylated primer in combination with one of the linker oligonucleotides, now functioning as a PCR primer. The convenience of CPCR is greatly enhanced by using a novel streptavidin-coated manifold, which is constructed so that it projects into each individual well of a microtiter plate. The procedure permits the simultaneous isolation of fragments from large numbers of DNA samples and minimizes the risk of contamination between reactions. We have applied this method to identify DNA sequences located downstream of known sequences in the human genome. The technique has also been used to identify end fragments of sequences cloned in a yeast artificial chromosome (YAC) vector. The reactions can be initiated directly from yeast colonies and provide access to DNA sequence information for these end fragments in a minimal number of steps. With the aid of the present technique, we have isolated over 100 end fragments from YACs derived from the human X chromosome. Isolated end sequences have been used to order YAC clones into a contig.

Deoxyribonucleic acid and cytological detection of Y-containing cells in an XX hypospadiac boy with polyorchidism

A hypospadiac boy with a hypoplastic penis and an apparent 46,XX karyotype in blood and testis cultures is described. Exploratory laparotomy and bilateral gonadal biopsy revealed the presence of 2 testes in the right and 1 in the left hemiscrotum, each of which only showed hypoplastic testicular tissues histologically. Uncultured testis smears showed Y chromatin in approximately 20% of the cells. Also, the Southern blot and polymerase chain reaction analyses detected a weak but distinct signal of Y chromosome-derived deoxyribonucleic acid sequences in the perineal skin but not in the blood lymphocytes. The results indicated that the boy had a small proportion of Y chromosome-containing cells in the form of mosaicism in limited tissues, such as the testes and perineal skin. This finding may have implications in the genesis of testes in some cases of XX patients, and true hermaphrodites or male pseudohermaphrodites with an apparent 46,XX karyotype. To our knowledge, this appears to be the first case of polyorchidism with an identified chromosome abnormality.

Absence of fetal cells in maternal circulation at a level of 1 in 25,000

A dual polymerase chain reaction (PCR) technique is developed which enables the detection of one part male DNA in 25,000 parts female DNA. The technique amplifies a part of the X-Y homologous amelogenin gene in which the Y counterpart has a 189 bp deletion within one of the introns. This deletion has made it possible to identify individual X and Y counterparts based on the difference in size between them. None of the 18 pregnant women studied showed a positive Y-signal although eight of them bear male fetuses excluding the presence of fetal cells at one in 25,000 maternal cells. The results presented here show that a sensitivity of greater than one in 25,000 is required for detection of fetal genetic disease using maternal peripheral blood.

A deletion in the amelogenin gene (AMG) causes X-linked amelogenesis imperfecta (AIH1)

Amelogenesis imperfecta is characterized by the defective formation of tooth enamel. Here we present evidence that the X-linked form of this disorder (AIH1) is caused by a structural alteration in one of the predominant proteins in enamel, amelogenin. Southern blot analysis revealed a deletion extending over 5 kb of the amelogenin gene in males with the hypomineralization form of the AIH1. Carrier females were heterozygous for the molecular defect. The deletion appears to include at least two exons of the amelogenin gene and the extent of the deletion was verified by PCR analysis. The mutation was shown to segregate with the disease among 15 analyzed individuals belonging to the same kindred. Our results link a defect in the amelogenin gene to the abnormal formation of enamel. We thus conclude that the amelogenin protein has a role in biomineralization of tooth enamel.

Molecular cloning and mapping of 10 new probes on the human Y chromosome

We have developed a novel positive cloning vector whose use precludes the cloning of any fragments less than 0.8 kb as well as 3.4-kb EcoRI fragments of DYZ1, the largest repeating-DNA family on the long arm of the human Y chromosome. Using this vector, we subcloned inserts of a Y-chromosome-specific phage library constructed from EcoRI-digested flow-sorted Y-chromosome DNA. Ten novel Y-specific fragments were obtained. Their localization on the Y chromosome was determined by deletion mapping using clinical samples with structurally abnormal Y chromosomes. The long arm of the Y chromosome was divided into 12 segments by the novel probes in combination with established probes. The amelogenin-like sequence, mapped on the long arm in Human Gene Mapping 10, has been mapped on the short arm.

Sex identification of forensic specimens by polymerase chain reaction (PCR): two alternative methods

Sex identification of forensic samples (bloodstains and decomposed tissue) by polymerase chain reaction (PCR) was investigated. Amplification of a segment of the amelogenin gene using a pair of primers revealed both Y- and X-specific bands at the same time. The gene has counterparts in both the X and Y chromosomes and a small deletion in the former made it possible to distinguish them. Analysis of the X-specific band is the most reliable method for sex identification. THe locus includes a single copy gene so a sample of 250 ng/tube of deoxyribonucleic acid (DNA) is required for identification. Amplification of part of the DYZ1 locus was attempted as an alternative method for analysis of infinitesimal amounts of sample. Even DNA from putrefied tissue could be analyzed by PCR because the locus consists of thousands of copies of repeating units pHY10.