First Records on Genetic Diversity and Population Structure of Algerian Peanut (Arachis hypogaea) Using Microsatellite Markers

Peanut (Arachis hypogaea L) is one of the wide cultivated plants with a narrow genetic base, hence the interest in prospecting, rescuing, and characterizing germplasm of this species is continuously carried out. In this work, eleven microsatellite markers were used to assess the genetic diversity and population structure of 68 Algerian peanut accessions originated from four geographic regions in the north and south of Algeria. A total of 83 alleles were amplified with a mean number of 7.545 alleles per locus and polymorphic information content (PIC) ranged from 0.625 to 0.874. The observed and expected heterozygosity varied from 0.31 to 1.00 and from 0.61 to 0.84 with a mean of 0.704 and 0.732, respectively. Genetic structure analysis showed a strong population at K?=?2, separating accessions according to their subspecies affiliation (hypogeae ssp. and fastigiata ssp.). It was also able to quantify the genetic correlations between genotypes using principal component analysis (PCA) and the method of groups of unweighted pairings with arithmetic means (UPGMA). Analysis of molecular variance (AMOVA) revealed high genetic variation within individuals (90.7%) and low genetic differentiation between subspecies (10.3%) and among populations (8.9%) from different geographical origin. Genetic diversity analysis in this study provides useful information for the exploration and utilization of these peanut cultivars.

     

Structural and Biochemical Basis for the Inhibitory Effect of Liprin-α3 on Mouse Diaphanous 1 (mDia1) Function

Diaphanous-related formins are eukaryotic actin nucleation factors regulated by an autoinhibitory interaction between the N-terminal RhoGTPase-binding domain (mDia_N) and the C-terminal Diaphanous-autoregulatory domain (DAD). Although the activation of formins by Rho proteins is well characterized, its inactivation is only marginally understood. Recently, liprin-α3 was shown to interact with mDia1. Overexpression of liprin-α3 resulted in a reduction of the cellular actin filament content. The molecular mechanisms of how liprin-α3 exerts this effect and counteracts mDia1 activation by RhoA are unknown. Here, we functionally and structurally define a minimal liprin-α3 core region, sufficient to recapitulate the liprin-α3 determined mDia1-respective cellular functions. We show that liprin-α3 alters the interaction kinetics and thermodynamics of mDia_N with RhoA·GTP and DAD. RhoA displaces liprin-α3 allosterically, whereas DAD competes with liprin-α3 for a highly overlapping binding site on mDia_N. Liprin-α3 regulates actin polymerization by lowering the regulatory potency of RhoA and DAD on mDia_N. We present a model of a mechanistically unexplored and new aspect of mDia_N regulation by liprin-α3.     

Meiotic Recombination in Arabidopsis Is Catalysed by DMC1, with RAD51 Playing a Supporting Role

Recombination establishes the chiasmata that physically link pairs of homologous chromosomes in meiosis, ensuring their balanced segregation at the first meiotic division and generating genetic variation. The visible manifestation of genetic crossing-overs, chiasmata are the result of an intricate and tightly regulated process involving induction of DNA double-strand breaks and their repair through invasion of a homologous template DNA duplex, catalysed by RAD51 and DMC1 in most eukaryotes. We describe here a RAD51-GFP fusion protein that retains the ability to assemble at DNA breaks but has lost its DNA break repair capacity. This protein fully complements the meiotic chromosomal fragmentation and sterility of Arabidopsis rad51, but not rad51 dmc1 mutants. Even though DMC1 is the only active meiotic strand transfer protein in the absence of RAD51 catalytic activity, no effect on genetic map distance was observed in complemented rad51 plants. The presence of inactive RAD51 nucleofilaments is thus able to fully support meiotic DSB repair and normal levels of crossing-over by DMC1. Our data demonstrate that RAD51 plays a supporting role for DMC1 in meiotic recombination in the flowering plant, Arabidopsis.     

Prognostic factors and survival in metastatic breast cancer: A single institution experience

Background

The current retrospective study aims to identify some determinants of survival in metastatic breast cancer.

Methods

The study concerned 332 patients with synchronous (SM) or metachronous (MM) metastatic breast cancer treated between January 2000 and December 2007. Statistical comparison between subgroups of patients concerning survival was carried out employing log-rank test for the invariable analysis and Cox model for the multivariable analysis. Factors included: age group (≤50 years vs. >50; ≤70 years vs. >70; ≤35 years vs. >35), menopausal status, presentation of metastatic disease (SM vs. MM), disease free interval (DFI) (≤24 months vs. >24 months; ≤60 months vs. >60 months), performance status at diagnosis of metastatic disease (PS) (0–1 vs. >1), hormone receptors (HR), number of metastatic sites (1 site vs. >1), nature of the metastatic site (visceral vs. non visceral), first line therapy, surgery of the primary tumor (SPT), locoregional radiotherapy (LRRT) and use or not of bisphosphonates.

Results

Overall survival at 5 years was 12%. Positive prognostic factors in univariate analysis were: age ≤ 70 years, hormono-dependence of the tumor, good PS (PS 0–1), less than two metastatic sites, no visceral metastases, DFI ≥ 24 months, SPT or LRRT. In multivariate analysis, favorable independent prognostic factors included: good PS (PS 0–1), absence of visceral metastases (liver, lung, brain) and age ≤ 70 years.

Conclusion

Many of the prognostic factors in metastatic breast cancer found in our study are known in the literature but some of them, like the application of locoregional treatment (radiotherapy or surgery) and the use of bisphosphonates, need to be further investigated in randomized clinical trials.     

Mitochondrial Mutations in Subjects with Psychiatric Disorders

A considerable body of evidence supports the role of mitochondrial dysfunction in psychiatric disorders and mitochondrial DNA (mtDNA) mutations are known to alter brain energy metabolism, neurotransmission, and cause neurodegenerative disorders. Genetic studies focusing on common nuclear genome variants associated with these disorders have produced genome wide significant results but those studies have not directly studied mtDNA variants. The purpose of this study is to investigate, using next generation sequencing, the involvement of mtDNA variation in bipolar disorder, schizophrenia, major depressive disorder, and methamphetamine use. MtDNA extracted from multiple brain regions and blood were sequenced (121 mtDNA samples with an average of 8,800x coverage) and compared to an electronic database containing 26,850 mtDNA genomes. We confirmed novel and rare variants, and confirmed next generation sequencing error hotspots by traditional sequencing and genotyping methods. We observed a significant increase of non-synonymous mutations found in individuals with schizophrenia. Novel and rare non-synonymous mutations were found in psychiatric cases in mtDNA genes: ND6, ATP6, CYTB, and ND2. We also observed mtDNA heteroplasmy in brain at a locus previously associated with schizophrenia (T16519C). Large differences in heteroplasmy levels across brain regions within subjects suggest that somatic mutations accumulate differentially in brain regions. Finally, multiplasmy, a heteroplasmic measure of repeat length, was observed in brain from selective cases at a higher frequency than controls. These results offer support for increased rates of mtDNA substitutions in schizophrenia shown in our prior results. The variable levels of heteroplasmic/multiplasmic somatic mutations that occur in brain may be indicators of genetic instability in mtDNA.     

Profilin1 activity in cerebellar granule neurons is required for radial migration in vivo

Neuron migration defects are an important aspect of human neuropathies. The underlying molecular mechanisms of such migration defects are largely unknown. Actin dynamics has been recognized as an important determinant of neuronal migration, and we recently found that the actin-binding protein profilin1 is relevant for radial migration of cerebellar granule neurons (CGN). As the exploited brain-specific mutants lacked profilin1 in both neurons and glial cells, it remained unknown whether profilin1 activity in CGN is relevant for CGN migration in vivo. To test this, we capitalized on a transgenic mouse line that expresses a tamoxifen-inducible Cre variant in CGN, but no other cerebellar cell type. In these profilin1 mutants, the cell density was elevated in the molecular layer, and ectopic CGN occurred. Moreover, 5-bromo-2′-deoxyuridine tracing experiments revealed impaired CGN radial migration. Hence, our data demonstrate the cell autonomous role of profilin1 activity in CGN for radial migration.