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. 2010 Sep 14;107(37):16320-4.
doi: 10.1073/pnas.1002176107. Epub 2010 Jul 26.

Deletion of TDP-43 down-regulates Tbc1d1, a gene linked to obesity, and alters body fat metabolism

Po-Min Chiang  1 , Jonathan Ling, Yun Ha Jeong, Donald L Price, Susan M Aja, Philip C Wong
Affiliations

Deletion of TDP-43 down-regulates Tbc1d1, a gene linked to obesity, and alters body fat metabolism

Po-Min Chiang et al. Proc Natl Acad Sci U S A. .

Abstract

Tat activating regulatory DNA-binding protein (Tardbp or TDP-43), a highly conserved metazoan DNA/RNA binding protein thought to be involved in RNA transcription and splicing, has been linked to the pathophysiology of amyotrophic lateral sclerosis and frontotemporal lobar degeneration and is essential for early embryonic development. However, neither the physiological role of TDP-43 in the adult nor its downstream targets are well defined. To address these questions, we developed conditional Tardbp-KO mice and embryonic stem (ES) cell models. Here, we show that postnatal deletion of Tardbp in mice caused dramatic loss of body fat followed by rapid death. Moreover, conditional Tardbp-KO ES cells failed to proliferate. Importantly, high-throughput DNA sequencing analysis on the transcriptome of ES cells lacking Tardbp revealed a set of downstream targets of TDP-43. We show that Tbc1d1, a gene known to mediate leanness and linked to obesity, is down-regulated in the absence of TDP-43. Collectively, our results establish that TDP-43 is critical for fat metabolism and ES cell survival.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Strategy and validation for the conditional deletion of Tardbp. (A) Targeting at the Tardbp locus and removal of neomycin resistance cassette. Exon 3 is floxed and can be removed upon cre recombinase induction. (P, probe for DNA blotting; E, respective exons; F, Frt sites; L, loxP sites; DTA, diphtheria toxin selection cassette; NeoR, neomycin selection cassette.) (B) DNA blot analysis of the control and targeted ES clones; an Xba I digest produced fragments of, respectively, approximately 22 kbp and approximately 8 kbp from the WT and targeted allele when labeled with the probe P in A. (C) Tissue lysates of livers and spinal cords harvested from control, Rosa26-ErCre;Tardbp+/F, and Rosa26-ErCre;TardbpF/F mice treated with tamoxifen for 8 d were subjected to protein blot analyses using antisera against TDP-43 and GAPDH. (D) Quantification of TDP-43 level (mean ± SEM) in the liver blots shown in C (n = 3 independent animals in each group). *P < 0.05, **P < 0.01, ***P < 0.001.
Fig. 2.
Fig. 2.
Phenotype of Tardbp conditional KO mice. (A) Cumulative body weight changes (in g, mean ± SEM) were compared in tamoxifen-treated control, Rosa26-ErCre;Tardbp+/F, and Rosa26-ErCre;TardbpF/F mice (n = 5 per group). D0, pretreatment. (B) Daily energy intakes (mean ± SEM) while on tamoxifen diet, n = 5. (C) RER (mean ± SEM) was monitored continuously from D0 (pretreatment) to day 7 (1 d before quantitative NMR measurement); n = 5. (D) Quantitative NMR measurement (mean ± SEM) of body fat in the three mouse groups as in A. Note the selective loss of fat mass in the KO mice, in contrast to lean mass. Black, blue, and red lines indicate control, Rosa26-ErCre;Tardbp+/F, and Rosa26-ErCre;TardbpF/F mice, respectively (n = 4 per group, including the two dead mice in the F/F group). (E) Mesenteric fatty tissues (arrows) in CAG-ErCre;Tardbp+/+, CAG-ErCre;Tardbp+/F, and CAG-ErCre;TardbpF/F mice. (F) H&E staining shows loss of fat content in the white (left column) and brown fat (right column). Immunohistochemical staining using the markers ATGL (second column) and PPAR-γ (third column) to visualize adipocytes found in the subcutaneous white fat. Arrows indicate adipocytes. *P < 0.05, **P < 0.01, ***P < 0.001. (Scale bar: 100 μm.)
Fig. 3.
Fig. 3.
TDP-43 is required for proliferation and survival of ES cells. (A) Targeting strategies for generation of inducible Tardbp-null (iTDPKO) ES cells. iTDPKOES cells contain one floxed Tardbp allele (floxed TDP) and one disrupted Tardbp allele (iCre), whereas cTDP ES cells contain one WT allele and one disrupted Tardbp allele (iCre). PCR analysis identified an 159-bp (denoted by A) or a 305-bp (denoted by B) fragment corresponding to the WT or floxed allele, respectively. (B and C) 4-HT–treated iTDPKOES cells fail to proliferate and undergo apoptosis. Photomicrographs (B) and survival (C) (three independent pairs, mean ± SEM) of the ES cells after 6 and 9 d of treatment with 4-HT. (Scale bar: 300 μm.)
Fig. 4.
Fig. 4.
Validation of targets identified through deep sequencing analysis. (A) Protein blot analysis of Tbc1d1 and rfc2 from extracts of iTDPKO ES cells treated with 4-HT. Note the dramatic reduction in levels of TDP-43 whereas PCNA is similar in iTDPKO compared with cTDP ES cells. Antisera against actin used as a loading control. (B) Protein blot analysis of Tbc1d1 (Upper) and Tardbp (Middle) in the skeletal muscles of control, CAG-ErCre;Tardbp+/F, and CAG-ErCre;TardbpF/F mice. Note the depletion of TDP-43 and Tbc1d1 in muscle of mice lacking Tardbp. (*P < 0.05, **P < 0.01, ***P < 0.001.)
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