SMN gene duplication and the emergence of the SMN2 gene occurred in distinct hominids: SMN2 is unique to Homo sapiens

The spinal muscular atrophy (SMA) region on chromosome 5q13 contains an inverted duplication of about 500 kb, and deleterious mutations in the survival motor neuron 1 (SMN1) gene cause SMA, a common lethal childhood neuropathy. We have used a number of approaches to probe the evolutionary history of these genes and show that SMN gene duplication and the appearance of SMN2 occurred at very distinct evolutionary times. Molecular fossil and molecular clock data suggest that this duplication may have occurred as recently as 3 million years ago in that the position and identity repetitive elements are identical for both human SMN genes and overall sequence divergence ranged from 0.15% to 0.34%. However, these approaches ignore the possibility of sequence homogenization by means of gene conversion. Consequently, we have used quantitative polymerase chain rection and analysis of allelic variants to provide physical evidence for or against SMN gene duplication in the chimpanzee, mankind's closest relative. These studies have revealed that chimpanzees have 2-7 copies of the SMN gene per diploid genome; however, the two nucleotides diagnostic for exons 7-8 and the SMNdelta7 mRNA product of the SMN2 gene are absent in non-human primates. In contrast, the SMN2 gene has been detected in all extant human populations studied to date, including representatives from Europe, the Central African Republic, and the Congo. These data provide conclusive evidence that SMN gene duplication occurred more than 5 million years ago, before the separation of human and chimpanzee lineages, but that SMN2 appears for the first time in Homo sapiens.     

贵州普定穿洞出土的一化石智人颅盖骨

1976年南京大学地理系俞锦标教授等在贵州省普定县进行野外调查时,在穿洞发现骨化石、烧骨、灰烬等。后于1979年,在有关方面的配合下,在洞口进行试掘,掘到1.5米深处,获得了一个破碎的智人颅盖骨化石。颅盖骨附近还有右上颌骨半块、单独的右上中门齿一枚。与头骨化石共生的有一些骨角器、烧骨和少量石器。这些材料俞教授等已作过报道和初步研究(俞锦标等,1983;俞锦标,1984)。不久前,俞教授把头盖骨化石供本人作古人类学研究之用,现报告如下。     

Homeobrain, a novel paired-like homeobox gene is expressed in the Drosophila brain

The homeobrain (hbn) gene is a new paired-like homeobox gene which is expressed in the embryonic brain and the ventral nerve cord. Expression of homeobrain initiates during the blastoderm stage in the anterior dorsal head primordia and the gene is persistently expressed in these cells which form parts of the brain during later embryonic stages. An additional weaker expression pattern is detected in cells of the ventral nerve cord from stage 11 on. The homeodomain in the Homeobrain protein is most similar to the Drosophila proteins DRx, Aristaless and Munster. In addition, the localized brain expression patterns of homeobrain and DRx resemble each other. Two other homeobox genes, orthopedia and DRx are clustered in the 57B region along with homeobrain. The current evidence indicates that homeobrain, DRx and orthopedia form a homeobox gene cluster in which all the members are expressed in specific embryonic brain subregions.     

Gamma-tubulin is present in Drosophila melanogaster and Homo sapiens and is associated with the centrosome

The mipA gene of A. nidulans encodes a newly discovered member of the tubulin superfamily of proteins, gamma-tubulin. In A. nidulans, gamma-tubulin is essential for nuclear division and microtubule assembly and is associated with the spindle pole body, the fungal microtubule organizing center. By low stringency hybridizations we have cloned cDNAs from D. melanogaster and H. sapiens, the predicted products of which share more than 66% amino acid identity with A. nidulans gamma-tubulin. gamma-Tubulin-specific antibodies stained centrosomes of Drosophila, human, and mouse cell lines. Staining was most intense in prophase through metaphase when microtubule assembly from centrosomes was maximal. These results demonstrate that gamma-tubulin genes are present and expressed in humans and flies; they suggest that gamma-tubulin may be a universal component of microtubule organizing centers; and they are consistent with an earlier hypothesis that gamma-tubulin is a minus-end nucleator of microtubule assembly.     

Hypertrophy of the acetabulo-cristal buttress in Homo sapiens

In the early 1970s, excavation at the King site, a contact period Mississippian village in northwest Georgia, yielded the skeletal remains of a robust male (King 65) possessing marked hypertrophy of the acetabulo-cristal buttress. The buttress is morphologically similar to that of Plio-Pleistocene Homo but it is accompanied by an anatomically modern degree of thickening of the gluteal table of the ilium. Although the degree of cortical thickness of the gluteal table of the ilium is apparently species-specific, hypertrophy of the acetabulo-cristal buttress is developmental and may be expressed in all species of Homo. © 1993 Wiley-Liss, Inc.     

Identification and molecular cloning Moplaa gene, a homologue of Homo sapiens PLAA, in Magnaporthe oryzae

Magnaporthe oryzae has been used as a model fungal pathogen to study the molecular basis of plant-fungus interactions due to its economic and genetic importance. In this study, we identified a novel gene, Moplaa, which is the homologue of Homo sapiens PLAA encoding a phospholipase A(2)-activating protein. Moplaa is conserved in some eukaryotic organisms by multiple alignment analysis. The function of the Moplaa gene was studied using the gene target replacement method. The Moplaa deletion mutant exhibited retarded growth and conidial germination, reduced conidiation, appressorial turgor pressure and pathogenicity to rice CO-39. Reintroduction of the gene restored defects of the Moplaa deletion mutant.     

Identification and molecular cloning Moplaa gene,a homologue of Homo sapiens PLAA,in Magnaporthe oryzae

Magnaporthe oryzae has been used as a model fungal pathogen to study the molecular basis of plant–fungus interactions due to its economic and genetic importance. In this study, we identified a novel gene, Moplaa, which is the homologue of Homo sapiens PLAA encoding a phospholipase A₂-activating protein. Moplaa is conserved in some eukaryotic organisms by multiple alignment analysis. The function of the Moplaa gene was studied using the gene target replacement method. The Moplaa deletion mutant exhibited retarded growth and conidial germination, reduced conidiation, appressorial turgor pressure and pathogenicity to rice CO-39. Reintroduction of the gene restored defects of the Moplaa deletion mutant.     

A novel repressor-type homeobox gene,ved, is involved in dharma/bozozok-mediated dorsal organizer formation in zebrafish

To gain insight into the genetic mechanisms of photoreceptor development, we analyzed a collection of zebrafish mutations characterized by early photoreceptor cell loss. The mutant defects impair outer segment formation and are accompanied by an abnormal distribution of visual pigments. Rods and different cone types display defects of similar severity suggesting that genetic pathways common to all photoreceptors are affected. To investigate whether these phenotypes involve cell–cell interaction defects, we analyzed genetically mosaic animals. Interaction of niezerka photoreceptors with wild-type tissues improves the survival of mutant cells and restores their elongated morphology. In contrast, cells carrying mutations in the loci brudas, elipsa, fleer, and oval retain their defective phenotypes in a wild-type environment indicating cell-autonomy. These experiments identify distinct phenotypic categories of photoreceptor mutants and indicate that zebrafish photoreceptor defects involve both cell-autonomous and cell-nonautonomous mechanisms.     

A genome-wide survey of alternative translational initiation events in Homo sapiens

Alternative translational initiation is an important mechanism to increase the diversity of gene products. Although some of alternative translational initiation events have been reported, such information remains anecdotal and does not allow for any generalizations. The number of the known alternative translational initiation genes is so few that we know little about its mechanism. There is a great demand to discover more alternative translational initiation genes. However, it is arduously time-consuming to discover novel alternative translational initiation genes by the experimental method. Therefore we systematically analyzed protein sequences available in public database and predicted 1237 protein clusters as potential alternative translational initiation events. We concluded that about 8%—10% of human genes have alternative translational initiation sites. The results significantly increased the number of alternative translation initiation events and indicated that alternative translation initiation is an important and general regulation mechanism in the cellular process.     

A genome-wide survey of alternative translational initiation events in Homo sapiens

Alternative translational initiation is an important mechanism to increase the diversity of gene products. Although some of alternative translational initiation events have been reported, such information remains anecdotal and does not allow for any generalizations. The number of the known alternative translational initiation genes is so few that we know little about its mechanism. There is a great demand to discover more alternative translational initiation genes. However, it is arduously time-consuming to discover novel alternative translational initiation genes by the experimental method. Therefore we systematically analyzed protein sequences available in public database and predicted 1237 protein clusters as potential alternative translational initiation events. We concluded that about 8%—10% of human genes have alternative translational initiation sites. The results significantly increased the number of alternative translation initiation events and indicated that alternative translation initiation is an important and general regulation mechanism in the cellular process.     

A retrotransposon-derived gene, PEG10, is a novel imprinted gene located on human chromosome 7q21

A novel paternally expressed imprinted gene, PEG10 (Paternally Expressed 10), was identified on human chromosome 7q21. PEG10 is located near the SGCE (Sarcoglycan epsilon) gene, whose mouse homologue was recently shown to be imprinted. Therefore, it is highly possible that a new imprinted gene cluster exists on human chromosome 7q21. Analysis of two predicted open reading frames (ORF1 and ORF2) revealed that ORF1 and ORF2 have homology to the gag and pol proteins of some vertebrate retrotransposons, respectively. These data suggest that PEG10 is derived from a retrotransposon that was previously integrated into the mammalian genome. PEG10 is likely to be essential for understanding how exogenous genes become imprinted.