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Chicken spindlin genes on W and Z chromosomes: transcriptional expression of both genes and dynamic behavior of spindlin in interphase and mitotic cells.

Contigs of genomic clones covering about 480 kb on the terminal region of the short arm of chicken W chromosome were obtained. By applying the exon trapping procedure on this whole region, a chicken homolog of spindlin gene, chSpin-W, was identified and subcloned. A counterpart gene, chSpin-Z, was found near the centromere on the long arm of Z chromosome. Although protein-coding regions of both genes are nearly identical, a part of the 3'-untranslated region is sufficiently different to distinguish the transcript of chSpin-W. Both chSpin-W and chSpin-Z are transcribed in early embryos. chSpin-Z is transcribed in various tissues of adult chickens, while chSpin-W is transcribed most prominently in ovarian granulosa and thecal cells. When female chicken embryonic fibroblasts were transfected with a cDNA construct for red fluorescent protein or green fluorescent protein-fused spindlin or FLAG-tagged spindlin, the expressed spindlin was co-localized with SUMO-1 in nuclear dots, ND10, in interphase cells, while the expressed spindlin was localized on entire chromosomes during mitosis. The localization of spindlin in ND10 reappeared after mitosis in daughter cell nuclei. A C-terminal region of spindlin was suggested to be required for the localization of spindlin to ND10.

Amino Acid Sequence↗

The DNA sequence and comparative analysis of human chromosome 20.

The finished sequence of human chromosome 20 comprises 59,187,298 base pairs (bp) and represents 99.4% of the euchromatic DNA. A single contig of 26 megabases (Mb) spans the entire short arm, and five contigs separated by gaps totalling 320 kb span the long arm of this metacentric chromosome. An additional 234,339 bp of sequence has been determined within the pericentromeric region of the long arm. We annotated 727 genes and 168 pseudogenes in the sequence. About 64% of these genes have a 5' and a 3' untranslated region and a complete open reading frame. Comparative analysis of the sequence of chromosome 20 to whole-genome shotgun-sequence data of two other vertebrates, the mouse Mus musculus and the puffer fish Tetraodon nigroviridis, provides an independent measure of the efficiency of gene annotation, and indicates that this analysis may account for more than 95% of all coding exons and almost all genes.

Animals↗

Identification of the familial cylindromatosis tumour-suppressor gene.

Familial cylindromatosis is an autosomal dominant genetic predisposition to multiple tumours of the skin appendages. The susceptibility gene (CYLD) has previously been localized to chromosome 16q and has the genetic attributes of a tumour-suppressor gene (recessive oncogene). Here we have identified CYLD by detecting germline mutations in 21 cylindromatosis families and somatic mutations in 1 sporadic and 5 familial cylindromas. All mutations predict truncation or absence of the encoded protein. CYLD encodes three cytoskeletal-associated-protein-glycine-conserved (CAP-GLY) domains, which are found in proteins that coordinate the attachment of organelles to microtubules. CYLD also has sequence homology to the catalytic domain of ubiquitin carboxy-terminal hydrolases (UCH).

Amino Acid Sequence↗

Analysis of expressed sequence tags indicates 35,000 human genes.

The number of protein-coding genes in an organism provides a useful first measure of its molecular complexity. Single-celled prokaryotes and eukaryotes typically have a few thousand genes; for example, Escherichia coli has 4,300 and Saccharomyces cerevisiae has 6,000. Evolution of multicellularity appears to have been accompanied by a several-fold increase in gene number, the invertebrates Caenorhabditis elegans and Drosophila melanogaster having 19,000 and 13,600 genes, respectively. Here we estimate the number of human genes by comparing a set of human expressed sequence tag (EST) contigs with human chromosome 22 and with a non-redundant set of mRNA sequences. The two comparisons give mutually consistent estimates of approximately 35,000 genes, substantially lower than most previous estimates. Evolution of the increased physiological complexity of vertebrates may therefore have depended more on the combinatorial diversification of regulatory networks or alternative splicing than on a substantial increase in gene number.

Alternative Splicing↗

Mutations in ATP6N1B, encoding a new kidney vacuolar proton pump 116-kD subunit, cause recessive distal renal tubular acidosis with preserved hearing.

The multi-subunit H+-ATPase pump is present at particularly high density on the apical (luminal) surface of -intercalated cells of the cortical collecting duct of the distal nephron, where vectorial proton transport is required for urinary acidification. The complete subunit composition of the apical ATPase, however, has not been fully agreed upon. Functional failure of -intercalated cells results in a group of disorders, the distal renal tubular acidoses (dRTA), whose features include metabolic acidosis accompanied by disturbances of potassium balance, urinary calcium solubility, bone physiology and growth. Mutations in the gene encoding the B-subunit of the apical pump (ATP6B1) cause dRTA accompanied by deafness. We previously localized a gene for dRTA with preserved hearing to 7q33-34 (ref. 4). We report here the identification of this gene, ATP6N1B, which encodes an 840 amino acid novel kidney-specific isoform of ATP6N1A, the 116-kD non-catalytic accessory subunit of the proton pump. Northern-blot analysis demonstrated ATP6N1B expression in kidney but not other main organs. Immunofluorescence studies in human kidney cortex revealed that ATP6N1B localizes almost exclusively to the apical surface of -intercalated cells. We screened nine dRTA kindreds with normal audiometry that linked to the ATP6N1B locus, and identified different homozygous mutations in ATP6N1B in eight. These include nonsense, deletion and splice-site changes, all of which will truncate the protein. Our findings identify a new kidney-specific proton pump 116-kD accessory subunit that is highly expressed in proton-secreting cells in the distal nephron, and illustrate its essential role in normal vectorial acid transport into the urine by the kidney.

Acidosis, Renal Tubular↗

Insertion of beta-satellite repeats identifies a transmembrane protease causing both congenital and childhood onset autosomal recessive deafness.

Approximately 50% of childhood deafness is caused by mutations in specific genes. Autosomal recessive loci account for approximately 80% of nonsyndromic genetic deafness. Here we report the identification of a new transmembrane serine protease (TMPRSS3; also known as ECHOS1) expressed in many tissues, including fetal cochlea, which is mutated in the families used to describe both the DFNB10 and DFNB8 loci. An 8-bp deletion and insertion of 18 monomeric (approximately 68-bp) beta-satellite repeat units, normally present in tandem arrays of up to several hundred kilobases on the short arms of acrocentric chromosomes, causes congenital deafness (DFNB10). A mutation in a splice-acceptor site, resulting in a 4-bp insertion in the mRNA and a frameshift, was detected in childhood onset deafness (DFNB8). This is the first description of beta-satellite insertion into an active gene resulting in a pathogenic state, and the first description of a protease involved in hearing loss.

Adult↗

Sequence and analysis of rice chromosome 4.

Rice is the principal food for over half of the population of the world. With its genome size of 430 megabase pairs (Mb), the cultivated rice species Oryza sativa is a model plant for genome research. Here we report the sequence analysis of chromosome 4 of O. sativa, one of the first two rice chromosomes to be sequenced completely. The finished sequence spans 34.6 Mb and represents 97.3% of the chromosome. In addition, we report the longest known sequence for a plant centromere, a completely sequenced contig of 1.16 Mb corresponding to the centromeric region of chromosome 4. We predict 4,658 protein coding genes and 70 transfer RNA genes. A total of 1,681 predicted genes match available unique rice expressed sequence tags. Transposable elements have a pronounced bias towards the euchromatic regions, indicating a close correlation of their distributions to genes along the chromosome. Comparative genome analysis between cultivated rice subspecies shows that there is an overall syntenic relationship between the chromosomes and divergence at the level of single-nucleotide polymorphisms and insertions and deletions. By contrast, there is little conservation in gene order between rice and Arabidopsis.

Arabidopsis↗

A primitive Y chromosome in papaya marks incipient sex chromosome evolution.

Many diverse systems for sex determination have evolved in plants and animals. One involves physically distinct (heteromorphic) sex chromosomes (X and Y, or Z and W) that are homozygous in one sex (usually female) and heterozygous in the other (usually male). Sex chromosome evolution is thought to involve suppression of recombination around the sex determination genes, rendering permanently heterozygous a chromosomal region that may then accumulate deleterious recessive mutations by Muller's ratchet, and fix deleterious mutations by hitchhiking as nearby favourable mutations are selected on the Y chromosome. Over time, these processes may cause the Y chromosome to degenerate and to diverge from the X chromosome over much of its length; for example, only 5% of the human Y chromosome still shows X-Y recombination. Here we show that papaya contains a primitive Y chromosome, with a male-specific region that accounts for only about 10% of the chromosome but has undergone severe recombination suppression and DNA sequence degeneration. This finding provides direct evidence for the origin of sex chromosomes from autosomes.

Alleles↗

The DNA sequence and comparative analysis of human chromosome 10.

The finished sequence of human chromosome 10 comprises a total of 131,666,441 base pairs. It represents 99.4% of the euchromatic DNA and includes one megabase of heterochromatic sequence within the pericentromeric region of the short and long arm of the chromosome. Sequence annotation revealed 1,357 genes, of which 816 are protein coding, and 430 are pseudogenes. We observed widespread occurrence of overlapping coding genes (either strand) and identified 67 antisense transcripts. Our analysis suggests that both inter- and intrachromosomal segmental duplications have impacted on the gene count on chromosome 10. Multispecies comparative analysis indicated that we can readily annotate the protein-coding genes with current resources. We estimate that over 95% of all coding exons were identified in this study. Assessment of single base changes between the human chromosome 10 and chimpanzee sequence revealed nonsense mutations in only 21 coding genes with respect to the human sequence.

Animals↗

The DNA sequence of the human X chromosome.

The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.

Animals↗

DNA sequence and analysis of human chromosome 8.

The International Human Genome Sequencing Consortium (IHGSC) recently completed a sequence of the human genome. As part of this project, we have focused on chromosome 8. Although some chromosomes exhibit extreme characteristics in terms of length, gene content, repeat content and fraction segmentally duplicated, chromosome 8 is distinctly typical in character, being very close to the genome median in each of these aspects. This work describes a finished sequence and gene catalogue for the chromosome, which represents just over 5% of the euchromatic human genome. A unique feature of the chromosome is a vast region of approximately 15 megabases on distal 8p that appears to have a strikingly high mutation rate, which has accelerated in the hominids relative to other sequenced mammals. This fast-evolving region contains a number of genes related to innate immunity and the nervous system, including loci that appear to be under positive selection--these include the major defensin (DEF) gene cluster and MCPH1, a gene that may have contributed to the evolution of expanded brain size in the great apes. The data from chromosome 8 should allow a better understanding of both normal and disease biology and genome evolution.

Animals↗

The DNA sequence, annotation and analysis of human chromosome 3.

After the completion of a draft human genome sequence, the International Human Genome Sequencing Consortium has proceeded to finish and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human chromosomes. Chromosome 3 comprises just four contigs, one of which currently represents the longest unbroken stretch of finished DNA sequence known so far. The chromosome is remarkable in having the lowest rate of segmental duplication in the genome. It also includes a chemokine receptor gene cluster as well as numerous loci involved in multiple human cancers such as the gene encoding FHIT, which contains the most common constitutive fragile site in the genome, FRA3B. Using genomic sequence from chimpanzee and rhesus macaque, we were able to characterize the breakpoints defining a large pericentric inversion that occurred some time after the split of Homininae from Ponginae, and propose an evolutionary history of the inversion.

Animals↗

An integrated metric physical map of human chromosome 19.

A metric physical map of human chromosome 19 has been generated. The foundation of the map is sets of overlapping cosmids (contigs) generated by automated fingerprinting spanning over 95% of the euchromatin, about 50 megabases (Mb). Distances between selected cosmid clones were estimated using fluorescence in situ hybridization in sperm pronuclei, providing both order and distance between contigs. An average inter-marker separation of 230 kb has been obtained across the non-centromeric portion of the chromosome. Various types of larger insert clones were used to span gaps between contigs. Currently, the map consists of 51 'islands' containing multiple clone types, whose size, order and relative distance are known. Over 450 genes, genetic markers, sequence tagged sites (STSs), anonymous cDNAs, and other markers have been localized. In addition, EcoRI restriction maps have been generated for > 41 Mb (approximately 83%) of the chromosome.

Base Sequence↗

Mutations in a newly identified GTPase gene cause autosomal dominant hereditary spastic paraplegia.

The hereditary spastic paraplegias (HSPs; Strümpell-Lorrain syndrome, MIM number 18260) are a diverse class of disorders characterized by insidiously progressive lower-extremity spastic weakness (reviewed in refs. 1-3). Eight autosomal dominant HSP (ADHSP) loci have been identified, the most frequent of which is that linked to the SPG4 locus on chromosome 2p22 (found in approximately 42%), followed by that linked to the SPG3A locus on chromosome 14q11-q21 (in approximately 9%). Only SPG4 has been identified as a causative gene in ADHSP. Its protein (spastin) is predicted to participate in the assembly or function of nuclear protein complexes. Here we report the identification of mutations in a newly identified GTPase gene, SPG3A, in ADHSP affected individuals.

Amino Acid Sequence↗

Breakpoint sequences of an 1;8 translocation in a family with Gilles de la Tourette syndrome.

Gilles de la Tourette syndrome (GTS) is a common, heritable neurological disorder manifested by chronic motor and vocal tics with childhood onset. Previous extensive linkage analysis failed to identify a GTS gene based on an autosomal dominant pattern of inheritance. Recently, a family was reported with a balanced chromosomal translocation t(1;8)(q21.1;q22.1) in family members with GTS or tics. Chromosome 8q22.1 was previously implicated in GTS by both association and linkage results. We therefore cloned and sequenced both translocation breakpoints from this family. The CBFA2T1 gene was identified 11 kb distal to the 8q22.1 breakpoint. Sequencing of CBFA2TI exons within 37 unrelated GTS patients failed to identify any mutations. However, it is possible that the translocation altered the expression of this gene or another nearby gene. Examination of the breakpoint sequences revealed a duplication of six nucleotides from chromosome 8 but no change in the chromosome 1 sequence. The sequences immediately flanking the breakpoints on the two chromosomes were modestly similar, but the breakpoints did not occur within known interspersed repeats. Our results add to our knowledge of the genetics of GTS and the mechanisms of balanced chromosomal translocations.

Bacteriophages↗

Organization of the chemokine genes in the human and mouse major clusters of CC and CXC chemokines: diversification between the two species.

Chemokines are a family of small cytokines that play essential roles in the directed migration of various types of leukocytes. Based on the arrangement of the conserved cysteine residues, they are classified into two major subfamilies, CXC and CC, and two minor subfamilies, C and CX3C. So far, more than 40 members of this family have been identified in humans. Strikingly, the majority of CXC chemokine genes and that of CC chemokine genes are closely clustered at chromosomes 4q12-21 and 17q11.2, respectively. Similarly, the mouse major CXC and CC chemokine gene clusters are located on chromosomes 5 and 11, respectively. In order to understand the evolutionary processes that generated large numbers of CXC and CC chemokine genes in the respective chromosomal sites, we have constructed BAC and YAC contigs covering the human and mouse major clusters of CXC and CC chemokine genes. The results reveal that the organizations of CXC and CC chemokine genes in the major clusters are quite diverged between the two species most probably due to very recent gene duplications and rearrangements. Our results provide an important insight into the evolutionary processes that generated the major chemokine gene clusters and also valuable information in assigning the orthologues between human and mouse major cluster chemokines.

Animals↗

Loss of expression of human spectrin src homology domain binding protein 1 is associated with 10p loss in human prostatic adenocarcinoma.

The gene encoding human spectrin Src homology domain binding protein 1, or Hssh3bp1, which is a marker of macropinocytic vesicles and a potential regulator of macropinocytosis, co-localizes to a YAC containing chromosome 10p sequences at loci D10S89 and D10S111 that are frequently deleted in prostate tumors. Expression of Hssh3bp1 was evaluated at the protein level in 17 paired normal and malignant prostate tumor samples using the monoclonal antibody 2G8 to Hssh3bp1. These experiments demonstrated that 4/6 tumors (67%) with 10p deletion failed to express Hssh3bp1 protein compared to 5/11 (46%) tumors with intact 10p. Thus, loss of Hssh3bp1 expression is concordant with allelic loss of adjacent 10p sequences in human prostate tumors. In addition, two prostate tumor cell lines contain an exon skipping mutation in the Hssh3bp1 gene that leads to the abnormal splicing of the mRNA and loss of a portion of Abl tyrosine kinase SH3 domain binding site in the protein. These data are consistent with a role for Hssh3bp1 as a candidate tumor suppressor gene inactivated during prostate tumorigenesis.

Adaptor Proteins, Signal Transducing↗