Meiosis genes in Daphnia pulex and the role of parthenogenesis in genome evolution

<p>Abstract</p> <p>Background</p> <p>Thousands of parthenogenetic animal species have been described and cytogenetic manifestations of this reproductive mode are well known. However, little is understood about the molecular determinants of parthenogenesis. The <it>Daphnia pulex </it>genome must contain the molecular machinery for different reproductive modes: sexual (both male and female meiosis) and parthenogenetic (which is either cyclical or obligate). This feature makes <it>D. pulex </it>an ideal model to investigate the genetic basis of parthenogenesis and its consequences for gene and genome evolution. Here we describe the inventory of meiotic genes and their expression patterns during meiotic and parthenogenetic reproduction to help address whether parthenogenesis uses existing meiotic and mitotic machinery, or whether novel processes may be involved.</p> <p>Results</p> <p>We report an inventory of 130 homologs representing over 40 genes encoding proteins with diverse roles in meiotic processes in the genome of <it>D. pulex</it>. Many genes involved in cell cycle regulation and sister chromatid cohesion are characterized by expansions in copy number. In contrast, most genes involved in DNA replication and homologous recombination are present as single copies. Notably, <it>RECQ2 </it>(which suppresses homologous recombination) is present in multiple copies while <it>DMC1 </it>is the only gene in our inventory that is absent in the <it>Daphnia </it>genome. Expression patterns for 44 gene copies were similar during meiosis <it>versus </it>parthenogenesis, although several genes displayed marked differences in expression level in germline and somatic tissues.</p> <p>Conclusion</p> <p>We propose that expansions in meiotic gene families in <it>D. pulex </it>may be associated with parthenogenesis. Taking into account our findings, we provide a mechanistic model of parthenogenesis, highlighting steps that must differ from meiosis including sister chromatid cohesion and kinetochore attachment.</p

From critters to cancers: bridging comparative and clinical research on oxygen sensing, HIF signaling, and adaptations towards hypoxia

The objective of this symposium at the First International Congress of Respiratory Biology (ICRB) was to enhance communication between comparative biologists and cancer researchers working on O(2) sensing via the HIF pathway. Representatives from both camps came together on August 13-16, 2006, in Bonn, Germany, to discuss molecular adaptations that occur after cells have been challenged by a reduced (hypoxia) or completely absent (anoxia) supply of oxygen. This brief "critters-to-cancer" survey discusses current projects and new directions aimed at improving understanding of hypoxic signaling and developing therapeutic interventions

Geriatric assessment is superior to oncologists’ clinical judgement in identifying frailty

Background: Frailty is a syndrome associated with increased vulnerability and an important predictor of outcomes in older cancer patients. Systematic assessments to identify frailty are seldom applied, and oncologists’ ability to identify frailty is scarcely investigated. Methods: We compared oncologists’ classification of frailty (onc-frail) based on clinical judgement with a modified geriatric assessment (mGA), and investigated associations between frailty and overall survival. Patients X70 years referred for medical cancer treatment were eligible. mGA-frailty was defined as impairment in at least one of the following: daily activities, comorbidity, polypharmacy, physical function or at least one geriatric syndrome (cognitive impairment, depression, malnutrition, falls). Results: Three hundred and seven patients were enroled, 288 (94%) completed the mGA, 286 (93%) were rated by oncologists. Median age was 77 years, 56% had metastases, 85% performance status (PS) 0–1. Overall, 104/286 (36%) were onc-frail and 140/288 (49%) mGA-frail, the agreement was fair (kappa value 0.30 (95% CI 0.19; 0.41)), and 67 mGA-frail patients who frequently had localised disease, good PS and received curative treatment, were missed by the oncologists. Only mGA-frailty was independently prognostic for survival (HR 1.61, 95% CI 1.14; 2.27; P¼0.007). Conclusions: Systematic assessment of geriatric domains is needed to aid oncologists in identifying frail patients with poor survival.publishedVersio