Arginine vasotocin neuronal phenotypes, telencephalic fiber varicosities, and social behavior in butterflyfishes (Chaetodontidae): potential similarities to birds and mammals

The neuropeptide arginine vasopressin (AVP) influences many social behaviors through its action in the forebrain of mammals. However, the function of the homologous arginine vasotocin (AVT) in the forebrain of fishes, specifically the telencephalon remains unresolved. We tested whether the density of AVT-immunoreactive (-ir) fiber varicosities, somata size or number of AVT-ir neuronal phenotypes within the forebrain were predictive of social behavior in reproductive males of seven species of butterflyfishes (family Chaetodontidae) in four phylogenetic clades. Similar to other fishes, the aggressive (often territorial) species in most cases had larger AVT-ir cells within the gigantocellular preoptic cell group. Linear discriminant function analyses demonstrated that the density of AVT-ir varicosities within homologous telencephalic nuclei to those important for social behavior in mammals and birds were predictive of aggressive behavior, social affiliations, and mating system. Of note, the density of AVT-ir varicosities within the ventral nucleus of the ventral telencephalon, thought to be homologous to the septum of other vertebrates, was the strongest predictor of aggressive behavior, social affiliation, and mating system. These results are consistent with the postulate that AVT within the telencephalon of fishes plays an important role in social behavior and may function in a similar manner to that of AVT / AVP in birds and mammals despite having cell populations solely within the preoptic area.     

植物同源异型枢基因的研究进展

植物同源异型枢基因是涉及到植物个体发育的一类重要转录因子编码基因.这类基因及其编码蛋白的结构具有明显的保守性,在植物中广泛存在,研究这类基因,对于揭示植物的发育机制具有重要意义.     

Selection on coding regions determined Hox7 genes evolution

The important role of Hox genes in determining the regionalization of the body plan of the vertebrates makes them invaluable candidates for evolutionary analyses regarding functional and morphological innovation. Gene duplication and gene loss led to a variable number of Hox genes in different vertebrate lineages. The evolutionary forces determining the conservation or loss of Hox genes are poorly understood. In this study, we show that variable selective pressures acted on Hox7 genes in different evolutionary lineages, with episodes of positive selection occurring after gene duplications. Tests for functional divergence in paralogs detected significant differentiation in a region known to modulate HOX7 protein activity. Our results show that both positive and negative selection on coding regions are influencing Hox7 genes evolution.     

Dosage regulation of Zea mays homeobox (ZmHox) genes and their relationship with the dosage-sensitive regulatory factors of Shrunken 1 (Sh1) in maize

In gene dosage studies on the expression of the maize Shrunken I gene several dosage-sensitive regulatory factors were identified that modulate Sh 1 mRNA levels in various aneuploids. ZmHox 1a and 1b have been shown to interact with the Sh1 promoter sequences in vitro. The present study was conducted to test whether these molecularly defined regulatory genes are subject to dosage modulation and to determine whether ZmHox 1a and 1b are involved with the dosage sensitive modification of Sh1 expression. The result was that ZmHox 1a and 1b were affected by several transacting dosage modifiers and that both genes exhibited a structural gene dosage effect but did not modulate Sh1 mRNA levels. For some chromosomal regions, a correlation was found between the dosage regulation of Sh1 and that of ZmHox 1a, while other effects were not correlated. The results suggest that the dosage effects on Sh1 are not mediated by ZmHox 1a or 1b, but interestingly Sh1 and ZmHox 1a share some dosage-regulatory effects. Dev Genet 20:67–73, 1997. © 1997 Wiley-Liss, Inc.     

同源盒基因A10编码蛋白的靶调节基因的筛选与鉴定

目的：筛选和鉴定同源盒基因A10编码蛋白（HOXA10）的靶调节基因。方法：以人子宫内膜细胞系AN3CA为实验对象,采用染色质免疫沉淀方法筛选HOXA10靶基因;采用平端克隆方法构建HOXA10靶基因库;采用DNA序列分析结合生物信息学方法鉴定HOXA10靶基因。结果：共获得含有HOXA10结合片段的克隆197个,选取插入片段大于100bp的质粒67个进行DNA序列分析,其中含有HOXA10结合序列TTAT的基因16个。结论：初步筛选出16个HOXA10候选靶基因,为进一步研究HOXA10的基因调节机理提供了新的思路。     

Retinoic acid affects patterning along the anterior–posterior axis of the ascidian embryo

Because retinoic acid (RA) is known to affect anterior-posterior patterning in vertebrate embryos, it was questioned whether it shows similar effects in a more primitive chordate, the ascidian Halocynthia roretzi . Ascidian embryos treated with RA exhibited truncated phenotypes in a dose-dependent manner similar to the anterior truncations seen in vertebrate embryos. The most severely affected larvae possessed a round trunk without the papillae characteristic of the anterior terminal epidermis. Retinoic acid also altered the expression of HrHox-1 and Hroth in a dose-dependent manner. Expression of HrHox-1 increased, whereas expression of Hroth decreased with increasing levels of RA. In treated embryos, HrHox-1 was first expressed pan-ectodermally, then degraded in all but specific regions of the embryo. By contrast, initiation of Hroth expression was not affected, but epidermal expression was lost while expression in the neural tube narrowed toward the anterior in tail-bud embryos. These alterations in the expression of homeobox genes appear to correlate closely to the morphological defects elicited by RA treatment, suggesting broad conservation of developmental patterning mechanisms within the Phylum Chordata.     

BrdU Birth Dating Can Produce Errors in Cell Fate Specification in Chick Brain Development

Birth dating neurons with bromodeoxyuridine (BrdU) labeling is an established methodwidely employed by neurobiologists to study cell proliferation in embryonic, postnatal,and adult brain. Birth dating studies in the chick dorsal telencephalon and the mammalianstriatum have suggested that these structures develop in a strikingly similar manner, inwhich neurons with the same birth date aggregate to form “isochronic clusters.” Here weshow that isochronic cluster formation in the chick dorsal telencephalon is an artifact.In embryos given standardly employed doses of BrdU, we observed isochronic clusters butfound that clusters were absent with BrdU doses close to the limits of detection. Inaddition, in situ hybridization experiments established that neurons in the clustersdisplay errors in cell type specification: BrdU cell clusters in nidopallium adopted amesopallial neuronal fate, mesopallial clusters were misspecified as nidopallial cells,and in some instances, the BrdU clusters failed to express neuronal differentiationmarkers characteristic of the dorsal telencephalon. These results demonstrate that thechick dorsal telencephalon does not develop by isochronic cluster formation and highlightthe need to test the integrity of BrdU-treated tissue with gene expression markers ofregional and cell type identity.     

复合同源异型结构的研究进展

含有同源异型结构（homeobox）的蛋白质是一大类DNA结合蛋白,在胚胎发育、基因表达调节、细胞分化、神经发生等方面发挥重要作用。近年来发现了同源异型框与其它结构域同时存在,如PAX、POU、LIM、OAR、CUT、ELK、bZIP、SIX、PHD-finger、Engrailed等,近来还发现它通过基因融合或基因失调控方式参与肿瘤的发生。本文对这些含有复合同源框的蛋白质和基因的类型、结构、功能等方面的研究进展进行综述。