Sox9 transactivation and testicular expression of a novel human gene, KIAA0800

HDAC4 inhibits cell-cycle progression and protects neurons from cell death

HDAC4 is a Class II histone deacetylase (HDAC) that is highly expressed in the brain, but whose functional significance in the brain is not known. We show that forced expression of HDAC4 in cerebellar granule neurons protects them against low potassium-induced apoptosis. HDAC4 also protects HT22 neuroblastoma cells from death induced by oxidative stress. HDAC4-mediated neuroprotection does not require its HDAC catalytic domain and cannot be inhibited by chemical inhibitors of HDACs. Neuroprotection by HDAC4 also does not require the Raf-MEK-ERK or the PI-3 kinase-Akt signaling pathways and occurs despite the activation of c-jun, an event that is generally believed to condemn neurons to die. The protective action of HDAC4 occurs in the nucleus and is mediated by a region that contains the nuclear localization signal. HDAC4 inhibits the activity of cyclin-dependent kinase-1 (CDK1) and the progression of proliferating HEK293T and HT22 cells through the cell cycle. Mice-lacking HDAC4 have elevated CDK1 activity and display cerebellar abnormalities including a progressive loss of Purkinje neurons postnatally in posterior lobes. Surviving Purkinje neurons in these lobes have duplicated soma. Furthermore, large numbers of cells within these affected lobes incorporate BrdU, indicating cell-cycle progression. These abnormalities along with the ability of HDAC4 to inhibit CDK1 and cell-cycle progression in cultured cells suggest that neuroprotection by HDAC4 is mediated by preventing abortive cell-cycle progression.

Arabidopsis DDB1-CUL4 ASSOCIATED FACTOR1 forms a nuclear E3 ubiquitin ligase with DDB1 and CUL4 that is involved in multiple plant developmental processes

The human DDB1-CUL4 ASSOCIATED FACTOR (DCAF) proteins have been reported to interact directly with UV-DAMAGED DNA BINDING PROTEIN1 (DDB1) through the WDxR motif in their WD40 domain and function as substrate-recognition receptors for CULLIN4-based E3 ubiquitin ligases. Here, we identified and characterized a homolog of human DCAF1/VprBP in Arabidopsis thaliana. Yeast two-hybrid analysis demonstrated the physical interaction between DCAF1 and DDB1 from Arabidopsis, which is likely mediated via the WD40 domain of DCAF1 that contains two WDxR motifs. Moreover, coimmunoprecipitation assays showed that DCAF1 associates with DDB1, RELATED TO UBIQUITIN-modified CUL4, and the COP9 signalosome in vivo but not with CULLIN-ASSOCIATED and NEDDYLATION-DISSOCIATED1, CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1), or the COP10-DET1-DDB1 complex, supporting the existence of a distinct Arabidopsis CUL4 E3 ubiquitin ligase, the CUL4-DDB1-DCAF1 complex. Transient expression of fluorescently tagged DCAF1, DDB1, and CUL4 in onion epidermal cells showed their colocalization in the nucleus, consistent with the notion that the CUL4-DDB1-DCAF1 complex functions as a nuclear E3 ubiquitin ligase. Genetic and phenotypic analysis of two T-DNA insertion mutants of DCAF1 showed that embryonic development of the dcaf1 homozygote is arrested at the globular stage, indicating that DCAF1 is essential for plant embryogenesis. Reducing the levels of DCAF1 leads to diverse developmental defects, implying that DCAF1 might be involved in multiple developmental pathways.

Nucleotide sequence and embryonic expression of quail and duck Sox9 genes

Sox9 is a member of the Sry-type HMG-box (Sox) gene family. It encodes a transcription factor and is thought to be important for sexual differentiation in chicken. In the present study we have isolated Sox9 cDNAs from quail and duck, and examined the expression patterns of the corresponding genes in early embryonic gonads by whole-mount in situ hybridization. We developed a polymerase chain reaction-based protocol to identify the sex of quail and duck embryos before its morphological manifestation. Sox9 expression was first detected on days 5 and 7 in the gonads of male quail and duck embryos, respectively, and was not apparent in female gonads at these stages. These expression patterns are similar to that of chicken Sox9. Our results thus suggest that the expression of quail and duck Sox9 is associated with testis differentiation.

Turning on the male – SRY, SOX9 and sex determination in mammals

The decision of the bi-potential gonad to develop into either a testis or ovary is determined by the presence or absence of the Sex-determining Region gene on the Y chromosome (SRY). Since its discovery, almost 13 years ago, the molecular role that SRY plays in initiating the male sexual development cascade has proven difficult to ascertain. While biochemical studies of clinical mutants and mouse genetic models have helped in our understanding of SRY function, no direct downstream targets of SRY have yet been identified. There are, however, a number of other genes of equal importance in determining sexual phenotype, expressed before and after expression of SRY. Of these, one has proven of central importance to mammals and vertebrates, SOX9. This review describes our current knowledge of SRY and SOX9 structure and function in the light of recent key developments.

Two alleles of the Sox9a2 in the rice field eel

A variety of strategies for sex determination mechanisms have been utilized in vertebrates. The Sox9 gene encodes a transcription factor that is critical for testis determination and chondrogenesis in vertebrates. We present here the polymorphisms of the Sox9a gene in population in the rice field eel, a fresh-water fish with naturally sex reversal characteristic from female via intersex into male during its life. Two alleles of the Sox9a2 were found in the population, which may potentially be associated with the dimorphic distribution of the male population of the rice field eel.