A new Pax gene,Pax-9, maps to mouse Chromosome 12

Members of the Pax gene family have recently been shown to play important roles in mouse embryogenesis. Of eight so far characterized Pax genes, three have been associated with mouse developmental mutants. Here we report the cloning of a new Pax gene, Pax-9. Most of the DNA sequence encoding the highly conserved paired domain has been determined and compared with previously known paired domains. This comparison classifies Pax-9 as a member of the same subgroup as Pax-1/undulated. By analysis of the segregation of a Pax-9 restriction fragment length polymorphism and a large number of simple sequence length polymorphisms in an interspecific C57BL/6 x Mus musculus mollosinus backcross, Pax-9 was mapped close to the D12Nds1 locus on the proximal part of Chromosome (Chr) 12.     

Pax: a murine multigene family of paired box-containing genes.

A murine multigene family has been identified that shares a conserved sequence motif, the paired box, with developmental control and tissue-specific genes of Drosophila. To date five murine paired box-containing genes (Pax genes) have been described and one, Pax-1, has been associated with the developmental mutant phenotype undulated. Here we describe the paired boxes of three novel Pax genes, Pax-4, Pax-5, and Pax-6. Comparison of the eight murine paired domains of the mouse, the five Drosophila paired domains, and the three human paired domains shows that they fall into six distinct classes: class I comprises Pox meso, Pax-1, and HuP48; class II paired, gooseberry-proximal, gooseberry-distal, Pax-3, Pax-7, HuP1, and HuP2; class III Pax-2, Pax-5, and Pax-8; class IV Pax-4; class V Pox neuro; and class VI Pax-6. Pax-1 and the human gene HuP48 have identical paired domains, as do Pax-3 and HuP2 as well as Pax-7 and HuP1, and are likely to represent homologous genes in mouse and man. Identical intron-exon structure and extensive sequence homology of their paired boxes suggest that several Pax genes represent paralogs. The chromosomal location of all novel Pax genes and of Pax-3 and Pax-7 has been determined and reveals that they are not clustered.     

Transgenic mice expressing PAX3-FKHR have multiple defects in muscle development, including ectopic skeletal myogenesis in the developing neural tube

The t(2;13) chromosomal translocation is found in the majority of human alveolar rhabdomyosarcomas (RMS). The resulting PAX3-FKHR fusion protein contains PAX3 DNA-binding domains fused to the potent transactivation domain of FKHR, suggesting that PAX3-FKHR functions to deregulate PAX3-specific target genes and signaling pathways. We previously developed transgenic mice expressing PAX3-FKHR under the control of mouse Pax3 regulatory sequences to test this hypothesis. We reported that PAX3-FKHR interferes with normal Pax3 developmental functions, with mice exhibiting neural tube and neural crest abnormalities that mimic those found in Pax3-deficient Splotch mice. Here we expanded those studies to show that developmental expression of PAX3-FKHR results in aberrant myogenesis in the developing somites and neural tube, leading to ectopic skeletal muscle formation in the mature spinal cord. Gene expression profiling indicated that PAX3-FKHR expression in the developing neural tube induces a myogenic pattern of gene expression at the expense of the normal neurogenic program. Somite defects in PAX3-FKHR transgenic animals resulted in skeletal malformations that included rib fusions and mis-attachments. As opposed to the neural tube defects, the severity of the rib phenotype was rescued by reducing Pax3 levels through mating with Splotch mice. Embryos from the transgenic line expressing the highest levels of PAX3-FKHR had severe neural tube defects, including exencephaly, and almost half of the embryos died between gestational ages E13.5-E15.5. Nearly all of the embryos that survived to term died after birth due to severe spina bifida, rather than the absence of a muscular diaphragm. These studies reveal a prominent role for PAX3-FKHR in disrupting Pax3 functions and in deregulating skeletal muscle development, suggesting that this fusion protein plays a critical role in the pathogenesis of␣alveolar RMS by influencing the commitment␣and differentiation of the myogenic cell lineage.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Pax-5 is expressed at the midbrain-hindbrain boundary during mouse development.

The murine paired-box-containing gene 5, Pax-5, is highly homologous to two other Pax genes, Pax-2 and Pax-8. The expression pattern of Pax-5 during mouse embryogenesis was examined by in situ RNA hybridization and compared to those of Pax-2 and Pax-8. Beginning at day 9.5 postcoitum (p.c.), Pax-5 was expressed in the developing brain, predominantly at the midbrain-hindbrain boundary, and in the neural tube. While the neural tube expression pattern overlapped completely with Pax-2 and Pax-8, the expression pattern in the brain was only partially overlapping. Unlike Pax-2 and Pax-8, Pax-5 was not expressed in the developing excretory system, thyroid, eye or ear. Our data suggest that Pax-5 has a role in the development of the central nervous system.     

The Gene for PAX7, a Member of the Paired-Box-Containing Genes, Is Localized on Human Chromosome Arm 1p36

The murine Pax-7 gene and the cognate human gene, formerly designated HuP1, are members of the multi-gene paired-box-containing class of developmental regulatory genes first identified in Drosophila. By analysis of somatic cell hybrids segregating human chromosomes, the gene encoding PAX7 was localized to human chromosome 1. Fluorescence in situ hybridization confirmed this assignment and allowed mapping of the gene to the terminal region of the short arm (1p36) of the chromosome. Additionally, these results confirm the extensive homology between human chromosome 1p and the distal segment of mouse chromosome 4, extending from bands C5 through E2.     

Ash2l-1调控小鼠卵黄囊早期造血

作为甲基转移酶MLL/SET1复合体的核心成分之一,ASH2L能够促进组蛋白H3K4me3修饰的形成,并在小鼠早期胚胎发育过程中行使重要功能.在小鼠中,由于启动子的选择性使用,Ash2l会转录成两种不同长度的转录本并形成两种蛋白质亚型:ASH2L-1和ASH2L-2.目前有关该基因在小鼠胚胎发育中的作用机制及不同亚型的功能还不清楚.本文利用CRISPR/Cas9技术特异敲除Ash2l-1并研究该亚型的生理学功能.研究结果发现,当Ash2l-1缺失时,小鼠胚胎在E9.5~E10.5时发生致死.特别是Ash2l-1-/-E9.5胚胎的卵黄囊血管和早期造血发育存在明显缺陷.转录组测序结果显示,Ash2l-1的缺失影响红细胞发育和成熟、血管发生和形成相关基因的表达.H3K4me3的CUT&RUN结果显示,在一些表达下调关键基因的启动子区,H3K4me3修饰水平出现下降.以上结果表明,Ash2l-1在小鼠卵黄囊的早期造血和血管形成过程中是必不可少的,它可能是通过调控关键基因启动子区的H3K4me3修饰水平而控制这些基因的表达,从而在相关过程中行使功能.     

Disruption of Supv3L1 damages the skin and causes sarcopenia, loss of fat, and death

Supv3L1 is a conserved and ubiquitously expressed helicase found in numerous tissues and cell types of many species. In human cells, SUPV3L1 was shown to suppress apoptotic death and sister chromatid exchange, and impair mitochondrial RNA metabolism and protein synthesis. In vitro experiments revealed binding of SUPV3L1 to BLM and WRN proteins, suggesting a role in genome maintenance processes. Disruption of the Supv3L1 gene in the mouse has been reported to be embryonic lethal at early developmental stages. We generated a conditional mouse in which the phenotypes associated with the removal of exon 14 can be tested in a variety of tissues. Disruption mediated by a Mx1 promoter-driven Cre displayed a postnatal growth delay, reduced lifespan, loss of adipose tissue and muscle mass, and severe skin abnormalities manifesting as ichthyosis, thickening of the epidermis, and atrophy of the dermis and subcutaneous tissue. Using a tamoxifen-activatable Esr1/Cre driver, Supv3L1 disruption resulted in growth retardation and aging phenotypes, including loss of adipose tissue and muscle mass, kyphosis, cachexia, and premature death. Many of the abnormalities seen in the Mx1-Cre mice, such as hyperkeratosis characterized by profound scaling of feet and tail, could also be detected in tamoxifen-inducible Cre mice. Conditional ablation of Supv3L1 in keratinocytes confirmed atrophic changes in the skin and ichthyosis-like changes. Together, these data indicate that Supv3L1 is important for the maintenance of the skin barrier. In addition, loss of Supv3L1 function leads to accelerated aging-like phenotypes.     

Comparative analysis of Pax-2 protein distributions during neurulation in mice and zebrafish.

Members of different vertebrate species share a number of developmental mechanisms and control genes, suggesting that they have similar genetic programs of development. We compared the expression patterns of the Pax-2 protein in Mus musculus and Brachydanio rerio to gain a better understanding of the evolution of developmental control genes. We found that the tissue specificity and the time course of Pax-2 expression relative to specific developmental processes are remarkably similar during the early development of the two organisms. The brain, the optic stalk, the auditory vesicle, the pronephros, and single cells in the spinal cord and the hindbrain express Pax-2 in both species. The Pax-2 expression domain in the prospective brain of E8 mouse embryos has not been described previously. Expression appears first during early neurulation at the junction between the midbrain and hindbrain. However, there are some differences in Pax-2 expression between the two species. Most notable, expression at the midbrain/hindbrain boundary is no longer detectable after E11 in the mouse. Using monoclonal antibodies, we could exclude that primary neurons express Pax-2 in the zebrafish spinal cord. Our results confirm that Pax genes are highly conserved both in sequences and in expression patterns, indicating that they may have a function during early development that has been conserved during vertebrate evolution.     

Pax3-FKHR knock-in mice show developmental aberrations but do not develop tumors

Alveolar rhabdomyosarcoma is a pediatric disease specified by the recurrent chromosome translocations t(2;13) and t(1;13). These translocations result in the formation of the PAX3-FKHR and PAX7-FKHR fusion genes, which are thought to play a causal role in the genesis of this disease. Although PAX3-FKHR exhibits transforming activity in immortalized fibroblast cell lines, a direct role of this fusion protein in tumorigenesis in vivo has not been shown. We determined whether expression of Pax3-FKHR in the mouse germ line would render these animals prone to the development of rhabdomyosarcomas. By targeting FKHR cDNA sequences into the Pax3 locus of embryonic stem cells, we used these cells to generate mice carrying a Pax3-FKHR knock-in allele. Despite low expression of the knock-in allele, heterozygous offspring of Pax3-FKHR chimeric mice showed developmental abnormalities. These included intraventricular septum defects, tricuspid valve insufficiency, and diaphragm defects, which caused congestive heart failure leading to perinatal death. In addition, Pax3-FKHR heterozygous offspring displayed malformations of some but not all hypaxial muscles. However, neither newborn heterozygous pups nor their chimeric parents showed any signs of malignancy. We conclude that the Pax3-FKHR allele causes lethal developmental defects in knock-in mice but might be insufficient to cause muscle tumors.     

Pax-6 origins – implications from the structure of two coral Pax genes

 Vertebrate Pax-6 and its Drosophila homolog eyeless play central roles in eye specification, although it is not clear if this represents the ancestral role of this gene class. As the most ”primitive” animals with true nervous systems, the Cnidaria may be informative in terms of the evolution of the Pax gene family. For this reason we surveyed the Pax gene complement of a representative of the basal cnidarian class (the Anthozoa), the coral Acropora millepora. cDNAs encoding two coral Pax proteins were isolated. Pax-Aam encoded a protein containing only a paired domain, whereas Pax-Cam also contained a homeodomain clearly related to those in the Pax-6 family. The paired domains in both proteins most resembled the vertebrate Pax-2/5/8 class, but shared several distinctive substitutions. As in most Pax-6 homologs and orthologs, an intron was present in the Pax-Cam locus at a position corresponding to residues 46/47 in the homeodomain. We propose a model for evolution of the Pax family, in which the ancestor of all of the vertebrate Pax genes most resembled Pax-6, and arose via fusion of a Pax-Aam-like gene (encoding only a paired domain) with an anteriorly-expressed homeobox gene resembling the paired -like class. Received: 25 February 1998/Accepted: 23 March 1998     

Pax-6, a murine paired box gene, is expressed in the developing CNS.

A multigene family of paired-box-containing genes (Pax genes) has been identified in the mouse. In this report, we describe the expression pattern of Pax-6 during embryogenesis and the isolation of cDNA clones spanning the entire coding region. The Pax-6 protein consists of 422 amino acids as deduced from the longest open reading frame and contains, in addition to the paired domain, a paired-type homeodomain. Beginning with day 8 of gestation, Pax-6 is expressed in discrete regions of the forebrain and the hindbrain. In the neural tube, expression is mainly confined to mitotic active cells in the ventral ventricular zone along the entire anteroposterior axis starting at day 8.5 of development. Pax-6 is also expressed in the developing eye, the pituitary and the nasal epithelium.