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Jessica B. Bessler, Kirthi C. Reddy, Michiko Hayashi, Jonathan Hodgkin and Anne M. Villeneuve
Chromatin-associated protein HIM-17 is known to function in the chromosomal events of meiotic prophase. Here the authors report that HIM-17 regulates the balance between germ cell proliferation and meiotic development. This function for HIM-17 is hidden under normal growth conditions, but is revealed by growth at high temperature or in a sensitized genetic background. These data suggest that HIM-17 plays an important role in buffering the mitosis/meiosis switch against environmental fluctuation, ensuring that germ cells respond appropriately to the activation state of GLP-1/Notch and other developmental cues under a variety of conditions.
Mlh1 deficiency in zebrafish results in male sterility and aneuploid as well as triploid progeny in females, pp. 1561–1569
Harma Feitsma, Marcelo C. Leal, Peter B. Moens, Edwin Cuppen and Rüdiger W. Schulz
The results presented in this article show that multiple solutions exist for meiotic cross-over/segregation problems. Males carrying a mutation in MLH1 are sterile due to an arrest in spermatogenesis, but mutant females are fully fertile. SNP-based chromosome analysis shows that these defects are caused by aneuploidy, resulting from a failure of homologs to properly disjoin at meiosis I. Surprisingly, an unexpected high percentage of progeny is fully triploid.
How repeatable are associations between polymorphisms in achaete–scute and bristle number variation in Drosophila?, pp. 1987–1997
Jonathan D. Gruber, Anne Genissel, Stuart J. Macdonald and Anthony D. Long
Association studies provide one avenue to assess the contribution of a SNP to quantitative trait variation. This article describes four different association tests that provide wildly different results. The polymorphism is in the achaete–scute complex, and it can influence bristle number. The association is clear in a set of isogenic lines derived from a wild population, but the direction of the effect is reversed in a recent cohort sample. A second large cohort sample yielded no significant association. When such large controlled Drosophila studies of association provide such inconsistent results, one wonders what will be found in human association studies.
Interaction of Epe1 with the heterochromatin assembly pathway in Schizosaccharomyces pombe, pp. 1549–1560
Sara Isaac, Julian Walfridsson, Tal Zohar, David Lazar, Tamar Kahan, Karl Ekwall and Amikam Cohen
The assembly of heterochromatin along eukaryotic chromosome is critical for chromosomal functions. But unrestricted, heterochromatin spreading is detrimental and may repress essential genes and tumor suppressor genes. This article presents a genetic analysis of Epe1, a protein that modulates heterochromatin spreading in fission yeast. Epe1 regulates gene expression by interacting with the gene silencing mechanism at the stage of histone deacetylation.
The sex-determining locus in the tiger pufferfish, Takifugu rubripes, pp. 2039–2042
Kiyoshi Kikuchi, Wataru Kai, Ayumi Hosokawa, Naoki Mizuno, Hiroaki Suetake, Kiyoshi Asahina and Yuzuru Suzuki
Although the genome of the tiger pufferfish (fugu) was well annotated, the primary sex-determining gene was not identified. In addition, the mode of sex determination in this species is poorly understood. The authors reveal that the sex of fugu is determined by a single region on linkage group 19 in an XX–XY system. These findings are a major breakthrough that may soon lead to the identification of a novel sex-determining gene.
Evolution of the male-determining gene SRY within the cat family Felidae, pp. 1855–1867
V. King, P. N. Goodfellow, A. J. Pearks Wilkerson, W. E. Johnson, S. J. O'Brien and J. Pecon-Slattery
SRY, a gene vital for male development, triggers the formation of testis in most placental mammals. Sequence comparison shows that SRY exhibits distinctly different patterns of evolution among eight cat lineages spanning 36 species. Two of the lineages display a strong signature of positive selection; other lineages display strong purifying selection. This unique pattern implies a dynamic interplay between selection during speciation and conservation of gene function.
The flamenco locus controls the gypsy and ZAM retroviruses and is required for Drosophila oogenesis, pp. 1615–1624
Maryvonne Mével-Ninio, Alain Pelisson, Jennifer Kinder, Ana Regina Campos and Alain Bucheton
The retrovirus gypsy in Drosophila is kept from running amok by the flamenco locus. Located close to the centromere of the X chromosome, this locus spans at least 130 kb of transposon-rich heterochromatin and is not yet delimited. Through the analysis of new mutations in this gene, the authors show that flam controls not only gypsy but also another retroelement, ZAM, which also functions in the ovary's follicular epithelium, the tissue where the gypsy and ZAM retroviruses are repressed.
Phylogenetic mapping of recombination hotspots in human immunodeficiency virus via spatially smoothed change-point processes, pp. 1773–1785
Vladimir N. Minin, Karin S. Dorman, Fang Fang and Marc A. Suchard
Human immunodeficiency virus (HIV) lineages undergo recombination in a manner that appears to be nonuniform along the genome. Estimation of recombination rates from DNA sequences of HIV samples is particularly tricky. This article presents a clever Bayesian approach that detects a recombination hotspot within the gag gene.
Epigenetic mechanisms for breakdown of self-incompatibility in interspecific hybrids, pp. 1965–1973
June B. Nasrallah, Pei Liu, Susan Sherman-Broyles, Renate Schmidt and Mikhail E. Nasrallah
Speciation in plant species following hybridization is a common phenomenon. It is promoted by self-fertilization, and for this to occur in interspecific hybrids self-incompatibility mechanisms must be overcome. The authors describe two epigenetic mechanisms by which the normally dominant self-incompatibility trait can be lost in interspecific hybrids. Plasticity of self-incompatibility in nascent interspecific hybrids may provide flexibility in the selection of mating system and may contribute to these hybrids' success in nature.
DPL-1 DP, LIN-35 Rb and EFL-1 E2F act with the MCD-1 zinc-finger protein to promote programmed cell death in Caenorhabditis elegans, pp. 1719–1733
Peter W. Reddien, Erik C. Andersen, Michael C. Huang and H. Robert Horvitz
Two novel cell death-promoting genes in Caenorhabditis elegans were identified: mcd-1, which encodes a zinc-finger protein, and dpl-1. Cells carrying mcd-1 or dpl-1 mutations can initiate death, but recover, raising the possibility that inhibiting human counterparts of these genes might reduce apoptosis in disease.
Novel mad2 alleles isolated in a Schizosaccharomyces pombe 
-tubulin mutant are defective in metaphase arrest activity, but remain functional for chromosome stability in unperturbed mitosis, pp. 1571–1584
Yoshie Tange and Osami Niwa
This article provides insight into the spindle assembly checkpoint. A cold-sensitive -tubulin mutant of fission yeast that is specifically impaired in microtubule dynamics in anaphase depends on several components of the spindle assembly checkpoint, such as Mad2. A screen for suppressors of the -tubulin mutant yielded novel mad2 mutants defective in arresting mitotic progression upon gross perturbation of the spindle. These results indicate that the Mad2 functions required for checkpoint arrest and chromosome stability are genetically discernible.
Related articles in Genetics:
-Tubulin Mutant Are Defective in Metaphase Arrest Activity, but Remain Functional for Chromosome Stability in Unperturbed Mitosis
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