Expression of p63 mRNA isoforms in normal human tissue.

This report describes the presence of different p63 isoforms in normal human tissue. The p63, expressed by basal cells of stratified epithelia and myoepithelial cells, is characterized by different mRNA isoforms formed by alternative splicing. Three isoforms were shown to act pro-apoptotically, while the remaining three isoforms are anti-apoptotic. Therefore a shift in a balance between different p63 isoforms might promote or inhibit normal and malignant growth. Our results show that in bone marrow, brain, colon, skeletal muscle, spleen and testis only pro-apoptotic p63 isoforms are expressed, whereas only anti-apoptotic isoforms are present in lung, placenta and salivary gland. In kidney, prostate, skin, thymus, trachea and uterus both variants are present. Presented results will allow in the future to compare p63 isoforms in various pathological processes with normal tissue pattern in order to evaluate the contribution of p63 isoform imbalance to the pathophysiology of various malignant diseases.

Levels of E2A protein expression in B cell precursors are stage-dependent and inhibited by stem cell factor (c-kit ligand).

OBJECTIVE: The E2A-encoded proteins E47 and E12 are crucial to the development of pro-B and pre-B cells. The expression of E2A protein and mRNA during early B lymphopoiesis was determined and effects of stem cell factor (SCF; Steel factor; c-kit ligand) on E2A expression were evaluated. MATERIALS AND METHODS: Ex vivo murine pro-B cells and pre-B cells were isolated and in vitro B cell precursors were derived after culture of bone marrow with rmIL-7. Levels of E2A proteins were determined by Western analysis and mRNA by RT-PCR. E2A expression in vitro was also assessed in cultures supplemented with IL-7 +/- recombinant murine SCF (rmSCF), insulin-like growth factor-1 (rhIGF-1), or Flt3-ligand (rhFlt3-L). Turnover of E2A proteins was assessed following cycloheximide treatment. RESULTS: Ex vivo, pro-B cells had lower E47 protein levels than did pre-B cells but had comparable E2A mRNA levels. E2A protein, but not mRNA, levels were reduced in pro-B cells upon culture in vitro with IL-7 + rmSCF. This was associated with increased turnover of E2A proteins. In contrast, culture with IL-7 + IGF-1 or Flt3-L had minimal effects on E2A protein levels. CONCLUSION: Pre-B cells expressed higher levels of E2A protein than did pro-B cells and this mainly resulted from posttranscriptional regulation. Exogenous SCF inhibited E2A protein, but not mRNA, expression in cultured B cell precursors, possibly by increasing E2A protein turnover. The capacity to respond to SCF may influence the levels of E2A during B-cell development.