Genetic and environmental factors in the etiology of esophageal atresia and/or tracheoesophageal fistula: An overview of the current concepts

Esophageal atresia and/or tracheoesophageal fistula (EA/TEF) are severe congenital anomalies. Although recent years have brought significant improvement in clinical treatment, our understanding of the etiology of these defects is lagging. Many genes and genetic pathways have been implicated in the development of EA/TEF, but only a few genes have been shown to be involved in humans, in animals, or in both. Extrapolating data from animal models to humans is not always straightforward. Environmental factors may also carry a risk, but the mechanisms are yet to be elucidated. This review gives an overview of the current state of knowledge about both genetic and environmental risk factors in the etiology of EA/TEF. Birth Defects Research (Part A) 2009. © 2009 Wiley‐Liss, Inc.     

应用乙二醇冷冻小鼠胚胎：优化和简化程序的探索

提高解冻胚胎的发育能力和简化冷冻解冻程序是胚胎冷冻研究的两大永恒的主题。尽管乙二醇（EG）广泛用于家畜胚胎冷冻,但很少用于冷冻小鼠和人胚胎。为数很少的以EG慢冻小鼠或人胚胎的研究均采用较为复杂的人胚冷冻程序,未见简化程序和用EG冷冻小鼠桑椹胚的报道。采用简单的牛胚胎冷冻程序研究了发育时期、EG浓度、平衡方法、添加蔗糖以及解冻后脱除EG等对小鼠胚胎冻后发育能力的影响。结果显示：（1）致密晚期桑椹胚冻后体外培养囊胚发育率（81.92%±2.24%）和孵出率（68.56％±2.43%）显著（P＜0.05)高于4-细胞、8-细胞胚胎和致密早期桑椹胚胎;（2）1.8mol/L EG冷冻小鼠致密晚期桑椹胚的囊胚发育和孵出率显著高于其它浓度;（3）在EG中平衡10min的冻后囊胚发育显著好于平衡5、20或30min;（4）两步平衡冷冻胚胎的囊胚发育率和孵出率显著高于一步平衡;（5）用EG冷冻小鼠胚胎无需添加蔗糖;（6）解冻后可不脱除EG;（7）冻后发育的早期囊胚和囊胚细胞数明显少于体内发育胚胎。因此,用EG冷冻小鼠胚胎的最佳方案为：致密晚期桑椹胚用1.8mol/L EG不添加蔗糖、两步平衡15min、以简单的牛胚胎冷冻程序冷冻解冻、解冻后不脱除EG直接培养或移植。     

A landscape of hairy and twisted: hunting for new trichome mutants in the Saskatoon Arabidopsis T‐DNA population

A total of 88 new Arabidopsis lines with trichome variation were recovered by screening 49,200 single‐seed descent T₃ lines from the SK activation‐tagged population and from a new 20,000‐line T‐DNA insertion population (called pAG). Trichome variant lines were classified into 12 distinct phenotype categories. Single or multiple T‐DNA insertion sites were identified for 89% of these mutant lines. Alleles of the well‐known trichome genes TRY, GL2 and TTG1 were recovered with atypical phenotype variation not reported previously. Moreover, atypical gene expression profiles were documented for two additional mutants specifying TRY and GL2 disruptions. In remaining mutants, ten lines were disrupted in genes coding for proteins not implicated in trichome development, five were disrupted in hypothetical proteins and 11 were disrupted in proteins with unknown function. The collection represents new opportunities for the plant biology community to define trichome development more precisely and to refine the function of individual trichome genes.     

Synergistic roles of BMP15 and GDF9 in the development and function of the oocyte-cumulus cell complex in mice: genetic evidence for an oocyte-granulosa cell regulatory loop

Bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) are oocyte-specific growth factors that appear to play key roles in granulosa cell development and fertility in most mammalian species. We have evaluated the role(s) of these paracrine factors in the development and function of both the cumulus cells and oocytes by assessing cumulus expansion, oocyte maturation, fertilization, and preimplantation embryogenesis in Gdf9+/-Bmp15-/- [hereafter, double mutant (DM)] mice. We found that cumulus expansion, as well as the expression of hyaluronon synthase 2 (Has2) mRNA was impaired in DM oocyte-cumulus cell complexes. This aberrant cumulus expansion was not remedied by coculture with normal wild-type (WT) oocytes, indicating that the development and/or differentiation of cumulus cells in the DM, up to the stage of the preovulatory luteinizing hormone (LH) surge, is impaired. In addition, DM oocytes failed to enable FSH to induce cumulus expansion in WT oocytectomized (OOX) cumulus. Moreover, LH-induced oocyte meiotic resumption was significantly delayed in vivo, and this delayed resumption of meiosis was correlated with the reduced activation of mitogen-activated protein kinase (MAPK) in the cumulus cells, thus suggesting that GDF9 and BMP15 also regulate the function of cumulus cells after the preovulatory LH surge. Although spontaneous in vitro oocyte maturation occurred normally, oocyte fertilization and preimplantation embryogenesis were significantly altered in the DM, suggesting that the full complement of both GDF9 and BMP15 are essential for the development and function of oocytes. Because receptors for GDF9 and BMP15 have not yet been identified in mouse oocytes, the effects of the mutations in the Bmp15 and Gdf9 genes on oocyte development and functions must be produced indirectly by first affecting the granulosa cells and then the oocyte. Therefore, this study provides further evidence for the existence and functioning of an oocyte-granulosa cell regulatory loop.     

Aldehyde reductase isozymes in the mouse: Evidence for two new loci and localization of Ahr-3 on chromosome 7

Evidence is presented for two new forms of mouse liver and kidney aldehyde reductase activity (designated AHR-3 and AHR-4) resolved using cellulose acetate electrophoresis zymogram techniques and stained by glyceraldehyde and NADPH as substrate and coenzyme, respectively. Activity variants were observed for those isozymes among inbred strains of mice and used in a genetic analyses to support a proposal for two new genetic loci (Ahr-3 and Ah-4) which control the activity phenotype for these isozymes. Segregation analysis indicated that these loci are separately localized on the mouse genome, with Ahr-3 positioned on the distal end of chromosome 7. Liver AHR-2 (or hexonate dehydrogenase) exhibited no detectable phenotypic variation among the 44 inbred strains of mice examined. The AHR-3 and AHR-4 isozymes were readily distinguished from AHR-1 [or aldehyde reductase A₂, described previously by Duley and Holmes (Biochem. Genet. 20:1067, 1982)], hexonate dehydrogenase (AHR-2), and alcohol dehydrogenase A₂ in terms of their differential substrate, coenzyme, and inhibitor specificities.     

Genetics and development of ocular oxidases in the mouse: evidence for a new locus (Eox-l) closely linked with the aldehyde oxidase loci on chromosome 1

Summary. Isoelectric focusing (IEF) and histochemical techniques were used to examine the genetics, postnatal development and biochemical properties of ocular oxidases (EOXs) among inbred strains of mice. The designation as EOX was made on a provisional basis, since the 'natural' substrate(s) for this enzyme have not been identified. Five major forms were resolved from adult animals, which exhibited high activity in murine lens and low activity in the cornea. An additional ocular oxidase was observed in neonatal animals. Genetic analyses demonstrated that one of these enzymes (EOX-1) is encoded by a locus (Eox-1) which is closely linked with, but distinct from, the aldehyde oxidase (Aox) gene complex on chromosome one of the mouse. These results support the proposal that ocular oxidases are distinct from the major liver AOXs in this organism.     

The temporal requirement for vitamin A in the developing eye: mechanism of action in optic fissure closure and new roles for the vitamin in regulating cell proliferation and adhesion in the embryonic retina

Mammalian eye development requires vitamin A (retinol, ROL). The role of vitamin A at specific times during eye development was studied in rat fetuses made vitamin A deficient (VAD) after embryonic day (E) 10.5 (late VAD). The optic fissure does not close in late VAD embryos, and severe folding and collapse of the retina is observed at E18.5. Pitx2, a gene required for normal optic fissure closure, is dramatically downregulated in the periocular mesenchyme in late VAD embryos, and dissolution of the basal lamina does not occur at the optic fissure margin. The addition of ROL to late VAD embryos by E12.5 restores Pitx2 expression, supports dissolution of the basal lamina, and prevents coloboma, whereas supplementation at E13.5 does not. Surprisingly, ROL given as late as E13.5 completely prevents folding of the retina despite the presence of an open fetal fissure, showing that coloboma and retinal folding represent distinct VAD-dependent defects. Retinal folding due to VAD is preceded by an overall reduction in the percentage of cyclin D1 positive cells in the developing retina, (initially resulting in retinal thinning), as well as a dramatic reduction in the cell adhesion-related molecules, N-cadherin and β-catenin. Reduction of retinal cell number combined with a loss of the normal cell-cell adhesion proteins may contribute to the collapse and folding of the retina that occurs in late VAD fetuses.     

Ethylisopropyl-amiloride: a new and highly potent derivative of amiloride for the inhibition of the Na+/H+ exchange system in various cell types

Ethylisopropyl-amiloride is 100 times more potent than amiloride for inhibiting the Na+/H+ exchanger of 3T3 fibroblasts, chick skeletal muscle cells and chick cardiac cells. Half-maximum effects, measured at 3 mM external Na+ are observed at 20-100 nM and 5 microM for ethylisopropyl-amiloride and amiloride respectively. As previously observed for amiloride, the effect of ethylisopropyl-amiloride is antagonized by external Na+ ions.     

HIV-1 protease molecular dynamics of a wild-type and of the V82F/I84V mutant: possible contributions to drug resistance and a potential new target site for drugs

The protease from type 1 human immunodeficiency virus (HIV-1) is a critical drug target against which many therapeutically useful inhibitors have been developed; however, the set of viral strains in the population has been shifting to become more drug-resistant. Because indirect effects are contributing to drug resistance, an examination of the dynamic structures of a wild-type and a mutant could be insightful. Consequently, this study examined structural properties sampled during 22 nsec, all atom molecular dynamics (MD) simulations (in explicit water) of both a wild-type and the drug-resistant V82F/I84V mutant of HIV-1 protease. The V82F/I84V mutation significantly decreases the binding affinity of all HIV-1 protease inhibitors currently used clinically. Simulations have shown that the curling of the tips of the active site flaps immediately results in flap opening. In the 22-nsec MD simulations presented here, more frequent and more rapid curling of the mutant's active site flap tips was observed. The mutant protease's flaps also opened farther than the wild-type's flaps did and displayed more flexibility. This suggests that the effect of the mutations on the equilibrium between the semiopen and closed conformations could be one aspect of the mechanism of drug resistance for this mutant. In addition, correlated fluctuations in the active site and periphery were noted that point to a possible binding site for allosteric inhibitors.