Retroposition of autosomal mRNA yielded testis-specific gene family on human Y chromosome.

Most genes in the human NRY (non-recombining portion of the Y chromosome) can be assigned to one of two groups: X-homologous genes or testis-specific gene families with no obvious X-chromosomal homologues. The CDY genes have been localized to the human Y chromosome, and we report here that they are derivatives of a conventional single-copy gene, CDYL (CDY-like), located on human chromosome 13 and mouse chromosome 6. CDY genes retain CDYL exonic sequences but lack its introns. In mice, whose evolutionary lineage diverged before the appearance of the Y-linked derivatives, the autosomal Cdyl gene produces two transcripts; one is expressed ubiquitously and the other is expressed in testes only. In humans, autosomal CDYL produces only the ubiquitous transcript; the testis-specific transcript is the province of the Y-borne CDY genes. Our data indicate that CDY genes arose during primate evolution by retroposition of a CDYL mRNA and amplification of the retroposed gene. Retroposition contributed to the gene content of the human Y chromosome, together with two other molecular evolutionary processes: persistence of a subset of genes shared with the X chromosome and transposition of genomic DNA harbouring intact transcription units.

Xq-Yq interchange resulting in supernormal X-linked gene expression in severely retarded males with 46,XYq- karyotype.

The critical importance of dosage compensation is underscored by a novel human syndrome ("XYXq syndrome") in which we have detected partial X disomy, demonstrated supernormal gene expression resulting from the absence of X inactivation, and correlated this overexpression with its phenotypic consequences. Studies of three unrelated boys with 46,XYq- karyotypes and anomalous phenotypes (severe mental retardation, generalized hypotonia and microcephaly) show the presence of a small portion of distal Xq on the long arm of the Y derivative. Cells from these boys exhibit twice-normal activity of glucose-6-phosphate dehydrogenase, a representative Xq28 gene product. In all three cases, the presence of Xq DNA on a truncated Y chromosome resulted from an aberrant Xq-Yq interchange occurring in the father's germline.

Functional coherence of the human Y chromosome.

A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences. All 12 genes, and six of eight NRY genes or families previously isolated by less systematic means, fell into two classes. Genes in the first group were expressed in many organs; these housekeeping genes have X homologs that escape X inactivation. The second group, consisting of Y-chromosomal gene families expressed specifically in testes, may account for infertility among men with Y deletions. The coherence of the NRY's gene content contrasts with the apparently haphazard content of most eukaryotic chromosomes.

Four evolutionary strata on the human X chromosome.

Human sex chromosomes evolved from autosomes. Nineteen ancestral autosomal genes persist as differentiated homologs on the X and Y chromosomes. The ages of individual X-Y gene pairs (measured by nucleotide divergence) and the locations of their X members on the X chromosome were found to be highly correlated. Age decreased in stepwise fashion from the distal long arm to the distal short arm in at least four "evolutionary strata." Human sex chromosome evolution was probably punctuated by at least four events, each suppressing X-Y recombination in one stratum, without disturbing gene order on the X chromosome. The first event, which marked the beginnings of X-Y differentiation, occurred about 240 to 320 million years ago, shortly after divergence of the mammalian and avian lineages.

Distribution of the cytoskeletal protein, Nestin, in acute leukemia.

Nestin is a neuroepithelial stem cell marker that is expressed in some types of tumor cells. Recent reports suggest that Nestin may be closely related to malignant cell proliferation and migration. Acute leukemia (AL) is characterized by a lack of differentiation, which results in uncontrolled proliferation in the bone marrow and accumulation of immature cells. The expression and function of Nestin in AL is unclear. We investigated Nestin immunohistochemical patterns of 87 patients that included 47 cases of acute myeloid leukemia (AML) and 40 cases of acute lymphoblastic leukemia (ALL), and 20 patients in complete remission (CR) from AML or ALL. We also investigated the clinico-pathological features of 87 cases of AL and their CR and overall survival (OS). Nestin was expressed in leukemic blasts and mature granulocytic cells in most cases (39/47) of AML. Conversely, Nestin was expressed in mature granulocytic cells in fewer cases (6/40) of ALL, but not in blasts. Nestin expression appeared in leukemic blasts of AML, but not ALL. Nestin expression in AML blast cells was not associated with CR or OS. We provide evidence that Nestin is expressed in AL and might be a useful immunohistochemical marker for identifying AML and ALL.

Motoneuron-specific NR3B gene: no association with ALS and evidence for a common null allele.

OBJECTIVE: The GRIN3B gene encodes NR3B, a motoneuron-specific member of the NMDA type of ionotropic glutamate receptors. NR3B reduces the Ca(2+)-permeability as well as the overall current of the receptor response and may thereby protect motoneurons against glutamate-mediated excitotoxicity. We tested whether genetic dysfunction of GRIN3B is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). METHODS: We searched for mutations in the GRIN3B coding region (3.1 kb) in 117 individuals with familial ALS and in 46 individuals with sporadic ALS. We genotyped the newly identified GRIN3B null allele and four "tag single nucleotide polymorphisms (SNPs)" at the GRIN3B locus in 342 individuals with sporadic ALS and in 374 matched controls. The GRIN3B null allele frequency was determined in 2,128 individuals from a worldwide panel of 42 populations. We furthermore compared the GRIN3B coding sequence in primates (human-macaque) and rodents (rat-mouse) to evaluate the molecular evolution of GRIN3B. RESULTS: Thirty-two SNPs, including 16 previously unreported SNPs, one 27-bp deletion, a polymorphic CAG repeat, and a 4-bp insertion (insCGTT), were identified. Mutational and case-control studies did not reveal variants that cause or modify disease in ALS. Intriguing is an insCGTT variant that truncates the protein at its amino terminus and results in a GRIN3B null allele. We demonstrated a global distribution of the null allele with allele frequencies ranging between 0 and 0.38, and we delineated a null allele specific haplotype of 9.89 kb. Comparative genomic analysis across four taxa demonstrated accelerated evolution of NR3B in primates. CONCLUSIONS: Our study supports the conclusions that 1) GRIN3B does not seem to be associated with familial or sporadic ALS, 2) the GRIN3B null allele is a common polymorphism, 3) the GRIN3B null allele has arisen once and early in human evolution, and 4) the GRIN3B gene belongs to a group of nervous system-related genes that have been subjected to faster evolution during evolution.

Nestin expression in different tumours and its relevance to malignant grade.

BACKGROUND: Nestin, an intermediate filament (IF) protein, is expressed in proliferating progenitor cells of developmental and regenerating tissues, and is identified as a neuroepithelial precursor cell marker. Recently, nestin was detected in some neoplasms such as glioma, ependymoma, melanoma, rhabdomyosarcoma, gastrointestinal stromal tumour (GIST), and testicular stromal tumour. Moreover, the expression intensity of nestin exhibited significant correlation with the malignant grade of glioma. AIMS: To detect the expression of nestin in different tumours and to analyse the relationship between the expression of nestin and the malignant grade of the tumours. METHODS: Formalin-fixed and paraffin-embedded surgical samples of neoplastic tissues were obtained from the Department of Pathology of Sun Yat-sen University. Histological analysis and immunohistochemical staining for nestin were performed. Histoscores were analysed by semi-quantitative evaluation. RESULTS: Nestin was expressed predominantly in the cytoplasm of angiosarcoma, pancreatic adenocarcinoma and GIST samples, and some tumour cells expressed in the nucleus. There was a statistically significant difference between the histoscore of nestin in high malignant GIST (2.2366 (0.6920)) and that in low malignant GIST (1.3783 (0.4268)) (p = 0.003); and also between that in high malignant angiosarcoma (1.9188 (0.2069)) and that in low malignant angiosarcoma (0.6474 (0.3273)) (p = 0.000). Cavernous angioma did not express nestin. The histoscore of nestin in high malignant pancreatic adenocarcinoma (7/14) was 1.1767 (0.4676), and that in low malignant pancreatic adenocarcinoma (3/8) was 0.6577 (0.0056) (no significant difference, p = 0.112). CONCLUSIONS: Results suggest that the expression of nestin may play an important role in the development of some neoplasms such as GIST and angiosarcoma.

A human sex-chromosomal gene family expressed in male germ cells and encoding variably charged proteins.

Approximately 12 X-Y homologous gene pairs have been identified in the non-recombining portions of human sex chromosomes. These X-Y gene pairs fall into two categories. In the first category, both X and Y homologs are ubiquitously expressed. In the second category, the X homolog is ubiquitously expressed, whereas the Y homolog is expressed exclusively in the testis. Here we describe a family of human X-Y genes that cannot be assigned to either category. Designated VCX / Y ( Variable Charge X / Y; VCY previously known as BPY1 ), this gene family has multiple members on both X and Y, and all appear to be expressed exclusively in male germ cells. Members of the VCX / Y family share a high degree of sequence identity, with the exception that a 30 nucleotide unit is tandemly repeated in X-linked members but is present only once in Y-linked members. These atypical features suggest that the VCX / Y family has evolved in a manner previously unrecognized for mammalian X-Y genes. We also found that a copy of VCX is present in CRI-S232, a previously described genomic fragment derived from the X chromosome. Studies have shown that aberrant recombination between arrays of CRI-S232-homologous repeats flanking the steroid sulfatase ( STS ) gene results in STS deletion, which is manifested clinically as X-linked ichthyosis. The revelation that CRI-S232 contains VCX offers a more precise description of the genetic etiology of X-linked ichthyosis: it results from aberrant recombination between VCX gene arrays that flank the STS locus.

The human Y chromosome, in the light of evolution.

Most eukaryotic chromosomes, akin to messy toolboxes, store jumbles of genes with diverse biological uses. The linkage of a gene to a particular chromosome therefore rarely hints strongly at that gene's function. One striking exception to this pattern of gene distribution is the human Y chromosome. Far from being random and diverse, known human Y-chromosome genes show just a few distinct expression profiles. Their relative functional conformity reflects evolutionary factors inherent to sex-specific chromosomes.

Apaf-1 deficiency and neural tube closure defects are found in fog mice.

The forebrain overgrowth mutation (fog) was originally described as a spontaneous autosomal recessive mutation mapping to mouse chromosome 10 that produces forebrain defects, facial defects, and spina bifida. Although the fog mutant has been characterized and available to investigators for several years, the underlying mutation causing the pathology has not been known. Because of its phenotypic resemblance to apoptotic protease activating factor-1 (Apaf-1) knockout mice, we have investigated the possibility that the fog mutation is in the Apaf-1 gene. Allelic complementation, Western blot analysis, and caspase activation assays indicate that fog mutant mice lack Apaf-1 activity. Northern blot and reverse transcription-PCR analysis show that Apaf-1 mRNA is aberrantly processed, resulting in greatly reduced expression levels of normal Apaf-1 mRNA. These findings are strongly suggestive of the fog mutation being a hypomorphic Apaf-1 defect and implicate neural progenitor cell death in the pathogenesis of spina bifida-a common human congenital malformation. Because a complete deficiency in Apaf-1 usually results in perinatal lethality and fog/fog mice more readily survive into adulthood, these mutants serve as a valuable model with which apoptotic cell death can be studied in vivo.