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The histone H3K9 demethylase Kdm3b is required for somatic growth and female reproductive function.

Liu Z, Chen X, Zhou S, Liao L, Jiang R, Xu J - Int. J. Biol. Sci. (2015)

Bottom Line: We found that Kdm3b ablation decreased IGFBP-3 expressed in the kidney by 53% and significantly reduced IGFBP-3 in the blood, which caused an accelerated degradation of IGF-1 and a 36% decrease in circulating IGF-1 concentration.We also found Kdm3b was highly expressed in the female reproductive organs including ovary, oviduct and uterus.Importantly, these female reproductive phenotypes were associated with significantly increased levels of H3K9me1/2/3 in the ovary and uterus.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA. ; 3. Institute of Cancer Prevention and Treatment, Harbin Medical University, Harbin, China.

ABSTRACT
Kdm3b is a Jumonji C domain-containing protein that demethylates mono- and di-methylated lysine 9 of histone H3 (H3K9me1 and H3K9me2). Although the enzyme activity of Kdm3b is well characterized in vitro, its genetic and physiological function remains unknown. Herein, we generated Kdm3b knockout (Kdm3bKO) mice and observed restricted postnatal growth and female infertility in these mice. We found that Kdm3b ablation decreased IGFBP-3 expressed in the kidney by 53% and significantly reduced IGFBP-3 in the blood, which caused an accelerated degradation of IGF-1 and a 36% decrease in circulating IGF-1 concentration. We also found Kdm3b was highly expressed in the female reproductive organs including ovary, oviduct and uterus. Knockout of Kdm3b in female mice caused irregular estrous cycles, decreased 45% of the ovulation capability and 47% of the fertilization rate, and reduced 44% of the uterine decidual response, which were accompanied with a more than 50% decrease in the circulating levels of the 17beta-estradiol. Importantly, these female reproductive phenotypes were associated with significantly increased levels of H3K9me1/2/3 in the ovary and uterus. These results demonstrate that Kdm3b-mediated H3K9 demethylation plays essential roles in maintenance of the circulating IGF-1, postnatal somatic growth, circulating 17beta-estradiol, and female reproductive function.

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Kdm3bKO mice exhibit lower serum IGF-1 without changing IGF-1 mRNA expression in the liver (Panels A and B), faster IGF-1 degradation in the blood circulation (Panel C), lower serum IGFBP-3 (Panel D), and decreased IGFBP-3 mRNA expression in the kidney (Panel E). All animals used in these experiments were 8-10 weeks old male mice. Kdm3b protein is detected by IHC in the kidney epithelial cells of WT mice but not in the kidney of Kdm3bKO mice (Panel F). The number of mice in each genotype group is indicated in each panel. In Panels B and E,the relative expression levels of IGF-1 and IGFBP-3 mRNAs were measured by qPCR. In Panel C, a human IGF-1 specific antibody in an ELISA kit was used to specifically measure the injected human IGF-1 at each time point. In Panel D, IGFBPs were measured by ligand blotting using 125I-IGF-1. *, p < 0.05 by Student's t test.
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Figure 3: Kdm3bKO mice exhibit lower serum IGF-1 without changing IGF-1 mRNA expression in the liver (Panels A and B), faster IGF-1 degradation in the blood circulation (Panel C), lower serum IGFBP-3 (Panel D), and decreased IGFBP-3 mRNA expression in the kidney (Panel E). All animals used in these experiments were 8-10 weeks old male mice. Kdm3b protein is detected by IHC in the kidney epithelial cells of WT mice but not in the kidney of Kdm3bKO mice (Panel F). The number of mice in each genotype group is indicated in each panel. In Panels B and E,the relative expression levels of IGF-1 and IGFBP-3 mRNAs were measured by qPCR. In Panel C, a human IGF-1 specific antibody in an ELISA kit was used to specifically measure the injected human IGF-1 at each time point. In Panel D, IGFBPs were measured by ligand blotting using 125I-IGF-1. *, p < 0.05 by Student's t test.

Mentions: Male and female newborn Kdm3bKO pups had comparable body weights to their WT littermates, but became significantly smaller starting on P4 and P2, respectively (Fig. 2A and B). Their small body size was maintained at a significant level through their lifespan (Fig. 2C and D). In agreement with their smaller body size, the average IGF-1 concentration in Kdm3bKO mouse sera was reduced 36% when compared with age-matched WT mouse sera (Fig. 3A). However, IGF-1 mRNA levels in the liver of Kdm3bKO mice were not significantly different from that in WT mice (Fig. 3B), suggesting that Kdm3b deficiency does not affect the growth hormone (GH)-regulated transcription of the IGF-1 gene and the low IGF-1 concentration in Kdm3bKO mouse sera may be caused by its fast degradation. To measure the degradation speed of IGF-1 in vivo, we injected an equal dose of human IGF-1 (hIGF-1) into WT and Kdm3bKO mice and monitored its change in the serum over a time course. At time 0 (before injection), no hIGF-1 was detected in both WT and Kdm3bKO mouse sera, indicating that the assay had no cross-reaction with the endogenous mouse IGF-1. In 20 minutes, hIGF-1 reached about 300 ng/ml in both WT and Kdm3b-/- mice, indicating that the intraperitoneally injected hIGF-1 was equally absorbed by both groups of mice. At the time points of 200 and 300 minutes, the serum hIGF-1 concentration was reduced 50% and 73% in WT mice, while it was reduced as much as 73% and 90% in Kdm3bKO mice when compared with that at the 20-minute time point. Statistical analysis indicated that hIGF-1 in Kdm3bKO mice was significantly lower than that in WT mice at the time point of 300 minutes. At the time point of 20 hours, the injected hIGF-1 was completely degraded in both types of mice (Fig. 3C). These results demonstrate that the circulating IGF-1 has a much shorter half-life in Kdm3bKO versus WT mice, which may partially explain the low IGF-1 concentrations and restricted somatic growth of Kdm3bKO mice.


The histone H3K9 demethylase Kdm3b is required for somatic growth and female reproductive function.

Liu Z, Chen X, Zhou S, Liao L, Jiang R, Xu J - Int. J. Biol. Sci. (2015)

Kdm3bKO mice exhibit lower serum IGF-1 without changing IGF-1 mRNA expression in the liver (Panels A and B), faster IGF-1 degradation in the blood circulation (Panel C), lower serum IGFBP-3 (Panel D), and decreased IGFBP-3 mRNA expression in the kidney (Panel E). All animals used in these experiments were 8-10 weeks old male mice. Kdm3b protein is detected by IHC in the kidney epithelial cells of WT mice but not in the kidney of Kdm3bKO mice (Panel F). The number of mice in each genotype group is indicated in each panel. In Panels B and E,the relative expression levels of IGF-1 and IGFBP-3 mRNAs were measured by qPCR. In Panel C, a human IGF-1 specific antibody in an ELISA kit was used to specifically measure the injected human IGF-1 at each time point. In Panel D, IGFBPs were measured by ligand blotting using 125I-IGF-1. *, p < 0.05 by Student's t test.
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Figure 3: Kdm3bKO mice exhibit lower serum IGF-1 without changing IGF-1 mRNA expression in the liver (Panels A and B), faster IGF-1 degradation in the blood circulation (Panel C), lower serum IGFBP-3 (Panel D), and decreased IGFBP-3 mRNA expression in the kidney (Panel E). All animals used in these experiments were 8-10 weeks old male mice. Kdm3b protein is detected by IHC in the kidney epithelial cells of WT mice but not in the kidney of Kdm3bKO mice (Panel F). The number of mice in each genotype group is indicated in each panel. In Panels B and E,the relative expression levels of IGF-1 and IGFBP-3 mRNAs were measured by qPCR. In Panel C, a human IGF-1 specific antibody in an ELISA kit was used to specifically measure the injected human IGF-1 at each time point. In Panel D, IGFBPs were measured by ligand blotting using 125I-IGF-1. *, p < 0.05 by Student's t test.
Mentions: Male and female newborn Kdm3bKO pups had comparable body weights to their WT littermates, but became significantly smaller starting on P4 and P2, respectively (Fig. 2A and B). Their small body size was maintained at a significant level through their lifespan (Fig. 2C and D). In agreement with their smaller body size, the average IGF-1 concentration in Kdm3bKO mouse sera was reduced 36% when compared with age-matched WT mouse sera (Fig. 3A). However, IGF-1 mRNA levels in the liver of Kdm3bKO mice were not significantly different from that in WT mice (Fig. 3B), suggesting that Kdm3b deficiency does not affect the growth hormone (GH)-regulated transcription of the IGF-1 gene and the low IGF-1 concentration in Kdm3bKO mouse sera may be caused by its fast degradation. To measure the degradation speed of IGF-1 in vivo, we injected an equal dose of human IGF-1 (hIGF-1) into WT and Kdm3bKO mice and monitored its change in the serum over a time course. At time 0 (before injection), no hIGF-1 was detected in both WT and Kdm3bKO mouse sera, indicating that the assay had no cross-reaction with the endogenous mouse IGF-1. In 20 minutes, hIGF-1 reached about 300 ng/ml in both WT and Kdm3b-/- mice, indicating that the intraperitoneally injected hIGF-1 was equally absorbed by both groups of mice. At the time points of 200 and 300 minutes, the serum hIGF-1 concentration was reduced 50% and 73% in WT mice, while it was reduced as much as 73% and 90% in Kdm3bKO mice when compared with that at the 20-minute time point. Statistical analysis indicated that hIGF-1 in Kdm3bKO mice was significantly lower than that in WT mice at the time point of 300 minutes. At the time point of 20 hours, the injected hIGF-1 was completely degraded in both types of mice (Fig. 3C). These results demonstrate that the circulating IGF-1 has a much shorter half-life in Kdm3bKO versus WT mice, which may partially explain the low IGF-1 concentrations and restricted somatic growth of Kdm3bKO mice.

Bottom Line: We found that Kdm3b ablation decreased IGFBP-3 expressed in the kidney by 53% and significantly reduced IGFBP-3 in the blood, which caused an accelerated degradation of IGF-1 and a 36% decrease in circulating IGF-1 concentration.We also found Kdm3b was highly expressed in the female reproductive organs including ovary, oviduct and uterus.Importantly, these female reproductive phenotypes were associated with significantly increased levels of H3K9me1/2/3 in the ovary and uterus.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA. ; 3. Institute of Cancer Prevention and Treatment, Harbin Medical University, Harbin, China.

ABSTRACT
Kdm3b is a Jumonji C domain-containing protein that demethylates mono- and di-methylated lysine 9 of histone H3 (H3K9me1 and H3K9me2). Although the enzyme activity of Kdm3b is well characterized in vitro, its genetic and physiological function remains unknown. Herein, we generated Kdm3b knockout (Kdm3bKO) mice and observed restricted postnatal growth and female infertility in these mice. We found that Kdm3b ablation decreased IGFBP-3 expressed in the kidney by 53% and significantly reduced IGFBP-3 in the blood, which caused an accelerated degradation of IGF-1 and a 36% decrease in circulating IGF-1 concentration. We also found Kdm3b was highly expressed in the female reproductive organs including ovary, oviduct and uterus. Knockout of Kdm3b in female mice caused irregular estrous cycles, decreased 45% of the ovulation capability and 47% of the fertilization rate, and reduced 44% of the uterine decidual response, which were accompanied with a more than 50% decrease in the circulating levels of the 17beta-estradiol. Importantly, these female reproductive phenotypes were associated with significantly increased levels of H3K9me1/2/3 in the ovary and uterus. These results demonstrate that Kdm3b-mediated H3K9 demethylation plays essential roles in maintenance of the circulating IGF-1, postnatal somatic growth, circulating 17beta-estradiol, and female reproductive function.

Show MeSH
Related in: MedlinePlus