The MLL family of histone methyltransferases maintains active chromatin domains by methylating histone H3 on lysine 4 (H3K4). How MLL complexes recognize specific chromatin domains in a temporal and tissue-specific manner remains unclear. We show that the DNA-binding protein PAX2 promotes assembly of an H3K4 methyltransferase complex through the ubiquitously expressed nuclear factor PTIP (pax transcription activation domain interacting protein). PTIP copurifies with ALR, MLL3, and other components of a histone methyltransferase complex. PTIP promotes assembly of the ALR complex and H3K4 methylation at a PAX2-binding DNA element. Without PTIP, Pax2 binds to this element but does not assemble the ALR complex. Embryonic lethal ptip-null mutants and conditional mutants both show reduced levels of methylated H3K4. Thus, PTIP bridges DNA-binding developmental regulators to histone methyltransferase-dependent epigenetic regulation.

The bone morphogenetic proteins (BMPs) profoundly affect embryonic development, differentiation and disease. BMP signaling is suppressed by cysteine-rich domain proteins, such as chordin, that sequester ligands from the BMP receptor. We describe a novel protein, KCP, with 18 cysteine-rich domains. Unlike chordin, KCP enhances BMP signaling in a paracrine manner. Smad1-dependent transcription and phosphorylated Smad1 (P-Smad1) levels are increased, as KCP binds to BMP7 and enhances binding to the type I receptor. In vivo, Kcp(-/-) mice are viable and fertile. Because BMPs have a pivotal role in renal disease, we examined the phenotype of Kcp(-/-) mice in two different models of renal injury. Kcp(-/-) animals show reduced levels of P-Smad1, are more susceptible to developing renal interstitial fibrosis, are more sensitive to tubular injury and show substantial pathology after recovery. The data indicate an important role for KCP in attenuating the pathology of renal fibrotic disease.

The Pax2 gene encodes a DNA binding protein with multiple functions in the developing intermediate mesoderm and urogenital tract. Loss of Pax2 in mice results in the complete absence of kidneys, ureters, and sex specific epithelial structures derived from the intermediate mesoderm in both males and females. In this report, we describe two new alleles of Pax2 created by inserting the Enhanced Green Fluorescent Protein coding region into the 5′ untranslated leader sequence. One allele is a hypomorph that generates less protein and exhibits structural defects in kidneys and ureters upon homozygosity. A second allele is a true null that can be used to image Pax2 expressing cells in a mutant background. Organ culture and embryo analyses point to a loss of epithelial cell polarity and increased mobility in cells that have deleted Pax2 function. These experiments provide new insight into the role of Pax2 protein levels in determining correct renal architecture and cell fate. These new Pax2 alleles are valuable genetic reagents for in vivo studies of urogenital development.

The preovulatory gonadotropin surge in the sheep was recently characterized by a divergent pattern of LH beta and FSH beta mRNAs immediately preceding this event. It is not clear whether this pattern is due to estradiol (E2), inhibin or other effectors. In this study, to determine if E2 may be involved in the divergent beta mRNA patterns seen during the surge, gonadotropin surges were induced in anestrous ewes (An) by E2 (An + E2) and several parameters were then measured. These included the amounts of alpha, LH beta, and FSH beta mRNAs, as assessed by solution hybridization assays, plus pituitary and serum gonadotropin concentrations. The values were compared with those observed in control, An ewes, to assess the effect of E2. The E2 treatment resulted in LH and FSH surges that appeared to be similar to the normal surges seen during the breeding season. Concomitantly, the E2 treatment lowered pituitary concentrations of FSH (P less than 0.05), while LH amounts did not change. Although the effect of E2 on gonadotropin subunit mRNA amounts varied depending upon the individual subunit, the changes that were observed paralleled changes reported during the preovulatory surge of the cycle. Specifically, alpha mRNA amounts increased significantly (P less than 0.001) while FSH beta mRNA amounts fell dramatically (P less than 0.001). Moreover, LH beta mRNA amounts were slightly increased, although not significantly by E2. These results demonstrate that E2 effects changes in the amounts of the gonadotropin subunit mRNAs during an induced gonadotropin surge in An ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin (PRL) mRNA concentrations were assessed by nucleic acid hybridization assays in pituitaries of ewes representing the defined stages of the ovine estrous cycle. Concomitantly, pituitary and serum PRL concentrations were measured in these ewes using radioimmunoassays. It was observed that PRL serum, pituitary and mRNA concentrations tended to increase near the time of the gonadotropin preovulatory surge, particularly between 24 hrs before behavioral estrus to 5 hours after estrus. However, the changes in PRL mRNA, serum and pituitary concentrations were shown not to be statistically significant. These data suggest that PRL production during the sheep estrous cycle is maintained without dramatic changes in synthesis or secretion.