Pituitary Adenylate Cyclase-activating Polypeptide (PACAP) Targets Down Syndrome Candidate Region 1 (DSCR1/RCAN1) to control Neuronal Differentiation

Pituitary adenylate cyclase-activating peptide (PACAP) is a neurotrophic peptide involved in a wide range of nervous functions, including development, differentiation, and survival, and various aspects of learning and memory. Here we report that PACAP induces the expression of regulator of calcineurin 1 (RCAN1, also known as DSCR1), which is abnormally expressed in the brains of Down syndrome patients. Increased RCAN1 expression is accompanied by activation of the PKA-cAMP response element-binding protein pathways. EMSA and ChIP analyses demonstrate the presence of a functional cAMP response element in the RCAN1 promoter. Moreover, we show that PACAP-dependent neuronal differentiation is significantly disturbed by improper RCAN1 expression. Our data provide the first evidence of RCAN1, a Down syndrome-related gene, as a novel target for control of the neurotrophic function of PACAP.     

Switching roles: the functional plasticity of adult tissue stem cells

Adult organisms have to adapt to survive, and the same is true for their tissues. Rates and types of cell production must be rapidly and reversibly adjusted to meet tissue demands in response to both local and systemic challenges. Recent work reveals how stem cell (SC) populations meet these requirements by switching between functional states tuned to homoeostasis or regeneration. This plasticity extends to differentiating cells, which are capable of reverting to SCs after injury. The concept of the niche, the micro‐environment that sustains and regulates stem cells, is broadening, with a new appreciation of the role of physical factors and hormonal signals. Here, we review different functions of SCs, the cellular mechanisms that underlie them and the signals that bias the fate of SCs as they switch between roles.     

Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop

Cassava (Manihot esculenta) is an allogamous, vegetatively propagated, Neotropical crop that is also widely grown in tropical Africa and Southeast Asia. To elucidate genetic diversity and differentiation in the crop's primary and secondary centers of diversity, and the forces shaping them, SSR marker variation was assessed at 67 loci in 283 accessions of cassava landraces from Africa (Tanzania and Nigeria) and the Neotropics (Brazil, Colombia, Peru, Venezuela, Guatemala, Mexico and Argentina). Average gene diversity (i.e., genetic diversity) was high in all countries, with an average heterozygosity of 0.5358 ± 0.1184. Although the highest was found in Brazilian and Colombian accessions, genetic diversity in Neotropical and African materials is comparable. Despite the low level of differentiation [F_st(theta) = 0.091 ± 0.005] found among country samples, sufficient genetic distance (1-proportion of shared alleles) existed between individual genotypes to separate African from Neotropical accessions and to reveal a more pronounced substructure in the African landraces. Forces shaping differences in allele frequency at SSR loci and possibly counterbalancing successive founder effects involve probably spontaneous recombination, as assessed by parent-offspring relationships, and farmer-selection for adaptation.Communicated by H.C. Becker     

Neuregulins: functions,forms, and signaling strategies

The neuregulins (NRGs) are cell-cell signaling proteins that are ligands for receptor tyrosine kinases of the ErbB family. The neuregulin family of genes has four members: NRG1, NRG2, NRG3, and NRG4. Relatively little is known about the biological functions of the NRG2, 3, and 4 proteins, and they are considered in this review only briefly. The NRG1 proteins play essential roles in the nervous system, heart, and breast. There is also evidence for involvement of NRG signaling in the development and function of several other organ systems, and in human disease, including the pathogenesis of schizophrenia and breast cancer. There are many NRG1 isoforms, raising the question "Why so many neuregulins?" Study of mice with targeted mutations ("knockout mice") has demonstrated that isoforms differing in their N-terminal region or in their epidermal growth factor (EGF)-like domain differ in their in vivo functions. These differences in function might arise because of differences in expression pattern or might reflect differences in intrinsic biological characteristics. While differences in expression pattern certainly contribute to the observed differences in in vivo functions, there are also marked differences in intrinsic characteristics that may tailor isoforms for specific signaling requirements, a theme that will be emphasized in this review.     

Genetic differentiation of Pseudoregma bambucicola population based on mtDNA COII gene

mtDNA COII gene sequences were identified and analyzed using different types of software, namely, MEGA5.0, DNAMAN, and DnaSP5.0 in four Chinese provinces, namely, Sichuan, Zhejiang, Guizhou and Shanghai. Analysis of molecular genetic variation and its genetic structure and differentiation, combined with NJ tree, MP tree analysis and analysis of molecular variance (AMOVA), at Fst = 0.0582 conclude that the genetic differentiation is low, gene flow is Nm = 8.0911, and gene exchange is sufficient. However, for the geographic populations of Pseudoregma bambucicola in the four provinces, their gene exchange is relatively weak at Nm = 0.8284, whereas the genetic differentiation is high at Fst = 0.3764. Based on the data, total nucleotide diversity between the populations is 0.00158 ± 0.00021. The results showed that the total population of Tajima’s D and Fu’s Fs results are D = ?0.885 and Fs = 0.226, respectively. The experimental numerical results showed that this total population is not significant (P > 0.10), indicating that nine different geographic populations are short-term. No expansion occurred in the internal population. This study provided a theoretical and practical basis for the comprehensive prevention and control of P. bambucicola.     

High-level phenotypic variations in populations of Armeniaca sibirica in Nei Mongol,China

Aims Our objectives were to determine the variations in phenotypic traits of Armeniaca sibirica populations and their spatial patterns. Methods We used nested variation, coefficient of variation, multi-comparison, correlation analysis and principal component analysis to analyze the 23 phenotypic traits for 130 individuals in 13 populations of A. sibirica. Important findings The results showed that there were significant differences in phenotypic variations among and within populations. The variation was greater among populations (47.15%) than within population (16.43%). The mean phenotypic differentiation coefficient was 73.03% among populations, indicating the variance among populations being the main source of the phenotypic variation. The average variation coefficient of 23 traits ranged from 7.01% to 27.23%, with an average of 14.28%. The variation coefficient of nutlet was highest (15.67%), and the variation coefficient of fruit was smallest (12.11%). The phenotypic diversity is highest in Wanjiagou Tumotezuoqi and smallest in Horqin, Right Front Banner Chaersen. Longitude, mean annual precipitation and sunshine duration were significantly correlated with major traits of phenotypic. The 13 populations could be divided into four groups according to the principal component analysis. Leaf traits of Wula Mountain and nutlet traits of Archorchin Banner were significantly correlated with ecological and geographic factors.     

苹果属小金海棠的遗传多样性初步研究

用RAPD技术建立了苹果属小金海棠（Malus xiaojinensis）2个自然分布区的3个群体内随机选取的30株树（10株／每群体）及其相应的子代实生苗共6个群体、60个样本植株的分子标记。通过对15个3承机引物产生的81条RAPD这的统计,计算了不同群体RAPD多态性带的数目。用TREECON软件分析了不同群体及所有个体间的遗传关系,并用AMOVA技术分析了物种的遗传变异。结果是15个引物在全部分析个体中产生了58条多态性带,平均每引物3.8条。现有分布3个群体及其相应的子代实生苗群体的平均多态性带的数目都为1.5条左右。其中平均多态性带的数目最低的群体仅有0.7条,最高的群体也只有2.5条。遗传关系分析表明,2个自然分布区的不同群体间存在遗传分化现象。AMOVA分析显示小金海棠的遗传变异有相当一部分来源于群体间。     

Population structure in Mediterranean islands and risk of genetic invasion in Culexpipiens L. (Diptera: Culicidae)

The mosquito Culex pipiens is subjected to organophosphate treatments in both Corsica and southern Sardinia, but the resistance gene A2-B2, which is currently in a worldwide expansion, has only reached Sardinia. In order to understand this situation, the genetic structure of populations sampled in Sardinia and Corsica was assessed using 15 isozymes. Two loci (HK1 and HK2) were not taken into account because of the possibility of selection. For trie other loci, statistical independence was not rejected for all possible pairs, and no deviation from Hardy-Weinberg expectations was apparent. Low but significant genie differentiation was present between Corsica and Sardinia, as well as between northern and southern Sardinia, despite a large number of effective migrants per generation. These results are discussed in the context of the high probability of extinction/recolonization of breeding sites, the flight migration ability of this mosquito, and the pleiotropic cost of insecticide resistances genes. It is concluded that A2-B2 resistance is unlikely to reach Corsica from southern Sardinia, unless accidental human transportation occurs.     

Effect of canavanine and other amino acid analogues on akinete formation in the cyanobacterium Anabaena cylindrica

Addition of the arginine analogue, canavanine, to cultures of nitrogen-fixing Anabaena cylindrica at the onset of akinete formation, resulted in the development of akinetes randomly distributed within the filament, in addition to those adjacent to heterocysts. The total frequency of akinetes increased up to five-fold. A feature of akinetes is their increased content of cyanophycin granules (an arginine-aspartic acid polymer) and addition of canavanine to cultures at an earlier stage resulted in entire filaments becoming agranular and containing agranular akinetes. The effects on akinete pattern appeared to be specific for canavanine since other amino acid analogues, although increasing the frequency of akinetes (approximately two-fold), had no effect on their position relative to heterocysts. In ammonia-grown, stationary phase cultures of A. cylindrica, akinetes were observed adjacent to proheterocysts and in positions more than 20 cells from any heterocyst. These observations indicate that nitrogen fixation and heterocysts are not essential for akinete formation in A. cylindrica, although the availability of a source of fixed nitrogen does appear to be a requirement.These results suggest that during exponential growth some aspect of the physiology of vegetative cells suppresses their development into akinetes and that the role of the heterocyst may not be one of direct stimulation of adjacent vegetative cells to form akinetes, but the removal or negation of the inhibition within them. A model for akinete formation and the involvement of canavanine is given.