Significant genetic admixture after reintroduction of peregrine falcon (<Emphasis Type="Italic">Falco peregrinus</Emphasis>) in Southern Scandinavia

The peregrine falcon (Falco peregrinus) population in southern Scandinavia was almost extinct in the 1970’s. A successful reintroduction project was launched in 1974, using captive breeding birds of northern and southern Scandinavian, Finnish and Scottish origin. We examined the genetic structure in the pre-bottleneck population using eleven microsatellite markers and compared the data with the previously genotyped captive breeding population and contemporary wild population. Museum specimens between 53 and 130 years old were analyzed. Despite an apparent loss of historical genetic diversity, the contemporary population shows a relatively high level of genetic variation. Considerable gene introgression from captive breeding stock used to repopulate the former range of southern Scandinavian peregrines may have altered the genetic composition of this population. Both the historical and contemporary northern and southern Scandinavian populations are genetically differentiated. The reintroduction project implemented in the region and the use of non-native genetic stock likely prevented the southern Scandinavian population from extinction and thus helped maintain the level of genetic diversity and prevent inbreeding depression. The population is rapidly increasing in numbers and range and shows no indication of reduced fitness or adaptive capabilities in the wake of the severe bottleneck and the reintroduction.     

锌指蛋白ZFP580在全反式维甲酸调节大鼠血管平滑肌细胞迁移中的作用及机制

目的:探讨锌指基因ZFP580在全反式维甲酸(ATRA)调节VSMCs迁移功能中的作用及其机制。方法:分离,培养并鉴定大鼠主动脉VSMCs;分别予以0、5、10、20 μmol/L ATRA刺激VSMCs 24h,以0 μmol/L ATRA组为对照组,观察不同溶度ATRA刺激不同时间对VSMCs迁移能力的影响或给予0、20 μmol/L ATRA刺激VSMCs 24、48、72h,观察ATRA刺激不同时间对VSMCs迁移能力的影响;QPCR及Western blot检测ATRA刺激VSMCs后ZFP580的mRNA和蛋白表达变化;应用ERK抑制剂PD98059抑制ERK的蛋白表达,观察ERK信号蛋白表达变化对ATRA刺激后ZFP580蛋白表达的影响;腺病毒转染技术获得过表达或低表达ZFP580的VSMCs,QPCR及Western blot检测MMP-2和MMP-9、ZFP580蛋白和mRNA表达水平。结果:分离的VSMCs在培养10d后,免疫荧光显示平滑肌细胞特异性标记物SM22α抗体阳性。与对照组相比,5、10、20 μmol/L ATRA预刺激分别降低了32%、43%和59%的VSMCs迁移能力;20 μmol/L ATRA刺激VSMCs与对照组相比,在24、48、72h分别降低49%、36%和22%细胞迁移能力。ZFP580的mRNA和蛋白表达随着ATRA刺激溶度的增加和刺激时间的延长而升高。ERK在ATRA刺激15min即显著升高,运用ERK抑制剂PD98059(20 μmol/L)预处理抑制ERK蛋白表达并降低了ATRA诱导ZFP580的蛋白表达。过表达ZFP580降低MMP-2和MMP-9的mRNA和蛋白表达,反之,低表达ZFP580则上调了MMP-2和MMP-9的mRNA和蛋白表达。结论:ATRA可通过ERK信号通路上调ZFP580的表达,而ZFP580通过调控MMP-2和MMP-9的表达参与ATRA对VSMCs迁移的抑制作用。     

稳定同位素技术在鲨鱼摄食和洄游行为研究中的应用

随着稳定同位素分析技术的不断成熟,其在生态学领域中的应用也增长迅速,并成为动物摄食生态学的重要研究工具.鲨鱼因其在生物系统进化过程中的独特地位和海洋生态系统中的重要作用已成为海洋食物网研究的重点,然而国内针对鲨鱼摄食习性和洄游行为等方面的研究仍处于起步阶段.本文在总结了国内外鲨鱼稳定同位素分析组织样品选取和样品预处理方法的基础上,系统归纳了稳定同位素技术在鲨鱼摄食生态学,尤其在其摄食和洄游行为研究领域中的应用,着重分析稳定同位素技术在鲨鱼稳定同位素判别值和更新速率、食性分析、营养级评估、洄游路径分析和生态位分布等核心问题上的应用现状和发展前景,以期为国内学者开展鲨鱼类基础生物、生态学研究提供有益参考.     

Role of cell surface metalloprotease MT1-MMP in epithelial cell migration over laminin-5

Laminin-5 (Ln-5) is an extracellular matrix substrate for cell adhesion and migration, which is found in many epithelial basement membranes. Mechanisms eliciting migration on Ln-5 need to be elucidated because of their relevance to tissue remodeling and cancer metastasis. We showed that exogenous addition of activated matrix metalloprotease (MMP) 2 stimulates migration onto Ln-5 in breast epithelial cells via cleavage of the gamma2 subunit. To investigate the biological scope of this proteolytic mechanism, we tested a panel of cells, including colon and breast carcinomas, hepatomas, and immortalized hepatocytes, selected because they migrated or scattered constitutively in the presence of Ln-5. We found that constitutive migration was inhibited by BB94 or TIMPs, known inhibitors of MMPs. Limited profiling by gelatin zymography and Western blotting indicated that the ability to constitutively migrate on Ln-5 correlated with expression of plasma membrane bound MT1-MMP metalloprotease, rather than secretion of MMP2, since MMP2 was not produced by three cell lines (one breast and two colon carcinomas) that constitutively migrated on Ln-5. Moreover, migration on Ln-5 was reduced by MT1-MMP antisense oligonucleotides both in MMP2+ and MMP2- cell lines. MT1-MMP directly cleaved Ln-5, with a pattern similar to that of MMP2. The hemopexin-like domain of MMP2, which interferes with MMP2 activation, reduced Ln-5 migration in MT1-MMP+, MMP2+ cells, but not in MT1-MMP+, MMP2- cells. These results suggest a model whereby expression of MT1-MMP is the primary trigger for migration over Ln-5, whereas MMP2, which is activated by MT1-MMP, may play an ancillary role, perhaps by amplifying the MT1-MMP effects. Codistribution of MT1-MMP with Ln-5 in colon and breast cancer tissue specimens suggested a role for this mechanism in invasion. Thus, Ln-5 cleavage by MMPs may be a widespread mechanism that triggers migration in cells contacting epithelial basement membranes.     

Inhibition of Filamin-A Reduces Cancer Metastatic Potential

Filamin-A cross-links actin filaments into dynamic orthogonal networks, and interacts with an array of proteins of diverse cellular functions. Because several filamin-A interaction partners are implicated in signaling of cell mobility regulation, we tested the hypothesis that filamin-A plays a role in cancer metastasis. Using four pairs of filamin-A proficient and deficient isogenic cell lines, we found that filamin-A deficiency in cancer cells significantly reduces their migration and invasion. Using a xenograft tumor model with subcutaneous and intracardiac injections of tumor cells, we found that the filamin-A deficiency causes significant reduction of lung, splenic and systemic metastasis in nude mice. We evaluated the expression of filamin-A in breast cancer tissues by immunohistochemical staining, and found that low levels of filamin-A expression in cancer cells of the tumor tissues are associated with a better distant metastasis-free survival than those with normal levels of filamin-A. These data not only validate filamin-A as a prognostic marker for cancer metastasis, but also suggest that inhibition of filamin-A in cancer cells may reduce metastasis and that filamin-A can be used as a therapeutic target for filamin-A positive cancer.     

A long winter for the Red Queen: rethinking the evolution of seasonal migration

This paper advances an hypothesis that the primary adaptive driver of seasonal migration is maintenance of site fidelity to familiar breeding locations. We argue that seasonal migration is therefore principally an adaptation for geographic persistence when confronted with seasonality – analogous to hibernation, freeze tolerance, or other organismal adaptations to cyclically fluctuating environments. These ideas stand in contrast to traditional views that bird migration evolved as an adaptive dispersal strategy for exploiting new breeding areas and avoiding competitors. Our synthesis is supported by a large body of research on avian breeding biology that demonstrates the reproductive benefits of breeding‐site fidelity. Conceptualizing migration as an adaptation for persistence places new emphasis on understanding the evolutionary trade‐offs between migratory behaviour and other adaptations to fluctuating environments both within and across species. Seasonality‐induced departures from breeding areas, coupled with the reproductive benefits of maintaining breeding‐site fidelity, also provide a mechanism for explaining the evolution of migration that is agnostic to the geographic origin of migratory lineages (i.e. temperate or tropical). Thus, our framework reconciles much of the conflict in previous research on the historical biogeography of migratory species. Although migratory behaviour and geographic range change fluidly and rapidly in many populations, we argue that the loss of plasticity for migration via canalization is an overlooked aspect of the evolutionary dynamics of migration and helps explain the idiosyncratic distributions and migratory routes of long‐distance migrants. Our synthesis, which revolves around the insight that migratory organisms travel long distances simply to stay in the same place, provides a necessary evolutionary context for understanding historical biogeographic patterns in migratory lineages as well as the ecological dynamics of migratory connectivity between breeding and non‐breeding locations.     

Adverse wind conditions during northward Sahara crossings increase the in‐flight mortality of Black‐tailed Godwits

Long‐distance migratory flights are predicted to be associated with higher mortality rates when individuals encounter adverse weather conditions. However, directly connecting environmental conditions experienced in‐flight with the survival of migrants has proven difficult. We studied how the in‐flight mortality of 53 satellite‐tagged Black‐tailed Godwits (Limosa limosa limosa) during 132 crossings of the Sahara Desert, a major geographical barrier along their migration route between The Netherlands and sub‐Saharan Africa, is correlated with the experienced wind conditions and departure date during both southward and northward migration. We show that godwits experienced higher wind assistance during southward crossings, which seems to reflect local prevailing trade winds. Critically, we found that fatal northward crossings (15 deaths during 61 crossings) were associated with adverse wind conditions. Wind conditions during migration can thus directly influence vital rates. Changing wind conditions associated with global change may thus profoundly influence the costs of long‐distance migration in the future.     

Myogenesis defect due to Toca-1 knockdown can be suppressed by expression of N-WASP

Skeletal muscle formation is a multistep process involving proliferation, differentiation, alignment and fusion of myoblasts to form myotubes which fuse with additional myoblast to form myofibers. Toca-1 (Transducer of Cdc42-dependent actin assembly), is an adaptor protein which activates N-WASP in conjunction with Cdc42 to facilitate membrane invagination, endocytosis and actin cytoskeleton remodeling. Expression of Toca-1 in mouse primary myoblasts and C2C12 myoblasts was up-regulated on day 1 of differentiation and subsequently down-regulated during differentiation. Knocking down Toca-1 expression in C2C12 cells (Toca-1^KD cells) resulted in a significant decrease in myotube formation and expression of shRNA-resistant Toca-1 in Toca-1^KD cells rescued the myogenic defect, suggesting that the knockdown was specific and Toca-1 is essential for myotube formation. Toca-1^KD cells exhibited elongated spindle-like morphology, expressed myogenic markers (MyoD and MyHC) and localized N-Cadherin at cell periphery similar to control cells suggesting that Toca-1 is not essential for morphological changes or expression of proteins critical for differentiation. Toca-1^KD cells displayed prominent actin fibers suggesting a defect in actin cytoskeleton turnover necessary for cell–cell fusion. Toca-1^KD cells migrated faster than control cells and had a reduced number of vinculin patches similar to N-WASP^KO MEF cells. Transfection of N-WASP-expressing plasmid into Toca-1^KD cells restored myotube formation of Toca-1^KD cells. Thus, our results suggest that Toca-1^KD cells have defects in formation of myotubes probably due to reduced activity of actin cytoskeleton regulators such as N-WASP. This is the first study to identify and characterize the role of Toca-1 in myogenesis.     

cxcr2基因修饰小鼠骨髓间充质干细胞的构建与鉴定

目的构建小鼠CXC型趋化因子受体2(CXCR2)基因cxcr2过表达的骨髓间充质干细胞(Bone marrow mes-enchymal stem cell,BMSC)并进行鉴定。方法全骨髓贴壁法分离培养小鼠BMSC,采用流式细胞术检测干细胞抗原1(stem cell antigen-1,SCA-1)、CD44、CD43、CD45、IA/IE表达率,并诱导成骨分化。以含有小鼠cxcr2的质粒为模版进行PCR扩增,将获得的cxcr2克隆到慢病毒载体,命名为p Lenti-cxcr2-GZ;将其与慢病毒包装质粒共转染HEK-293T细胞,收获慢病毒后,通过离心法感染BMSC,经过1μg/mL zeocin压力选择建立了稳定表达CXCR2的小鼠BMSC(CXCR2-BMSC)。采用流式细胞术和RT-PCR分别检测其CXCR2蛋白和m RNA表达水平,Transwell趋化实验检测其迁移能力。结果 90%以上的第3代BMSC表达CD44、SCA-1,几乎不表达IA/IE、CD34、CD45,且成功诱导成骨分化。菌液PCR、质粒双酶切后,琼脂糖凝胶电泳鉴定结果得到特异、大小正确的条带及测序鉴定正确,表明成功构建了p Lenti-cxcr2-GZ表达质粒。流式细胞术和RT-PCR结果显示,CXCR2-BMSC的CXCR2蛋白和m RNA表达水平均明显高于对照组BMSC,差异有统计学意义(P<0.001)。Transwell结果显示,CXCR2-BMSC迁移能力高于对照组BMSC,差异有统计学意义(P<0.01)。结论利用慢病毒系统成功构建了稳定表达CXCR2的BM-SC,cxcr2基因修饰BMSC后可明显增加BMSC的迁移能力。     

VEGF guides angiogenic sprouting utilizing endothelial tip cell filopodia

Vascular endothelial growth factor (VEGF-A) is a major regulator of blood vessel formation and function. It controls several processes in endothelial cells, such as proliferation, survival, and migration, but it is not known how these are coordinately regulated to result in more complex morphogenetic events, such as tubular sprouting, fusion, and network formation. We show here that VEGF-A controls angiogenic sprouting in the early postnatal retina by guiding filopodial extension from specialized endothelial cells situated at the tips of the vascular sprouts. The tip cells respond to VEGF-A only by guided migration; the proliferative response to VEGF-A occurs in the sprout stalks. These two cellular responses are both mediated by agonistic activity of VEGF-A on VEGF receptor 2. Whereas tip cell migration depends on a gradient of VEGF-A, proliferation is regulated by its concentration. Thus, vessel patterning during retinal angiogenesis depends on the balance between two different qualities of the extracellular VEGF-A distribution, which regulate distinct cellular responses in defined populations of endothelial cells.