Expression of Runx2 transcription factor in non‐skeletal tissues, sperm and brain

Abstract

Runx2 is a master transcription factor for chondrocyte and osteoblast differentiation and bone formation. However expression of Runx2 (by RT-PCR), has been reported in non-skeletal tissues such as breast, T cells and testis. To better define Runx2 activity in non-skeletal tissues, we examined transgenic (Tg) mice expressing LacZ gene under control of 3.0 kb (3 Kb Tg) or 1.0 kb (1 Kb Tg) of the Runx2 distal (P1) promoter, Runx2 LacZ knock-in (Runx2 +/LacZ ) and Runx2/P1 LacZ knock-in (Runx2/P +/LacZ ). In the Runx2 3 Kb Tg mouse, β-galactosidase (β-gal) expression appeared in various non-skeletal tissues including testis, skin, adrenal gland and brain. β-gal expression from both 3 Kb and 1 Kb Tg, reflecting activity of the Runx2 promoter, was readily detectable in seminiferous tubules of the testis and the epididymis. At the single cell level, β-gal was detected in spermatids and mature sperms not in sertoli or Leydig cells. We also detected a positive signal from the Runx2 +/LacZ and Runx2/P1 +/LacZ mice. Indeed, Runx2 expression was observed in isolated mature sperms, which was confirmed by RT-PCR and western blot analysis. Runx2, however, was not related to sex determination and sperm motility. Runx2 mediated β-gal activity is also found robustly in the hippocampus and frontal lobe of the brain in Runx2 +/LacZ . Collectively, these results indicate that Runx2 is expressed in several non-skeletal tissues particularly sperms of testis and hippocampus of brain. It suggests that Runx2 may play an important role in male reproductive organ testis and brain.

An essential role of discoidin domain receptor 2 (DDR2) in osteoblast differentiation and chondrocyte maturation via modulation of Runx2 activation

“…More important, the disclosure of DDR2/Runx2 signaling may facilitate the identification of more DDR2 target genes in other cells or tissues that express functional Runx2, such as breast cancer cells, sperm, and brain. (56)(57)(58)(59) Therefore, it can be envisioned that the infertility phenotype in Ddr2 mutant mice might be associated with impaired Runx2 activity. (34) Among several candidate protein kinases, only ERK MAPK signaling was linked to DDR2 activation.…”

Runx2 Protein Stabilizes Hypoxia-inducible Factor-1α through Competition with von Hippel-Lindau Protein (pVHL) and Stimulates Angiogenesis in Growth Plate Hypertrophic Chondrocytes

“…Animals were maintained on a 12-h light/ 12-h dark cycle at 22-25°C under specific pathogen-free conditions and fed with standard chow and water ad libitum. Genotyping of Runx2 null and heterozygote mice was performed as described previously (31).…”

The Gene for Aromatase, a Rate-Limiting Enzyme for Local Estrogen Biosynthesis, Is a Downstream Target Gene of Runx2 in Skeletal Tissues

“…Animals were maintained on a 12-h light-12-h darkness cycle at 22°C to 25°C under specific-pathogen-free (SPF) conditions and fed with standard rodent chow and water ad libitum. Genotyping of Runx2 null and Runx2⌬C mice was performed as previously described (10). For sex determinations, genomic DNA from pups was obtained and analyzed for the presence of Sry by PCR as previously described (10).…”

“…Genotyping of Runx2 null and Runx2⌬C mice was performed as previously described (10). For sex determinations, genomic DNA from pups was obtained and analyzed for the presence of Sry by PCR as previously described (10).…”