Lomberk, Gwen A

AbstractBackgroundKleefstra Syndrome (KS) (MIM# 610253) is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase‐1 (EHMT1, GLP). EHMT1 (MIM# 607001) encodes a histone methyltransferase that heterodimerizes with EHMT2 (also known as G9a, MIM# 604599), which together are responsible for mono‐ and dimethylation of H3 lysine 9 (H3K9me1 and ‐me2), resulting in transcriptional repression of target genes.MethodsThis report describes an 18‐year‐old woman with intellectual disability, severely limited speech, hypotonia, microcephaly, and facial dysmorphisms, who was found to have a novel de novo single‐base frameshift deletion in EHMT1.ResultsFunctional studies using patient fibroblasts showed decreased H3K9me2 compared to wild‐type control cells, thus providing a rapid confirmatory test that complements molecular studies.ConclusionWhole exome sequencing revealed a novel frameshift deletion in EHMT1 after a lengthy diagnostic odyssey in this patient. Functional testing using this patient's fibroblasts provides proof‐of‐concept for the analysis of variants of uncertain significance that are predicted to impact EHMT1 enzymatic activity.

Krüppel-like factor (KLF)-10 is an important transcriptional regulator of TGF-β1signaling in both CD8+and CD4+T lymphocytes. In the present study, we demonstrate a novel role for KLF10 in the regulation of TGFβRII expression with functional relevance in macrophage differentiation and activation. We first show that transfer of KLF10−/−bone marrow-derived macrophages into wild-type (WT) mice leads to exacerbation of experimental colitis. At the cell biological level, using two phenotypic strategies, we show that KLF10-deficient mice have an altered colonic macrophage phenotype with higher frequency of proinflammatory LyC6+MHCII+cells and a reciprocal decrease of the anti-inflammatory LyC6−MHCII+subset. Additionally, the anti-inflammatory CD11b+CX3CR1hisubset of colonic macrophages is significantly decreased in KLF10−/−compared with WT mice under inflammatory conditions. Molecularly, CD11b+colonic macrophages from KLF10−/−mice exhibit a proinflammatory cytokine profile with increased production of TNF-α and lower production of IL-10 in response to LPS stimulation. Because KLF10 is a transcription factor, we explored how this protein may regulate macrophage function. Consequently, we analyzed the expression of TGFβRII expression in colonic macrophages and found that, in the absence of KLF10, macrophages express lower levels of TGFβRII and display an attenuated Smad-2 phosphorylation following TGF-β1stimulation. We further show that KLF10 directly binds to the TGFβRII promoter in macrophages, leading to enhanced gene expression through histone H3 acetylation. Collectively, our data reveal a critical role for KLF10 in the epigenetic regulation of TGFβRII expression in macrophages and the acquisition of a “regulatory” phenotype that contributes to intestinal mucosal homeostasis.

KLF10 has recently elicited significant attention as a transcriptional regulator of transforming growth factor-β1 (TGF-β1) signaling in CD4+ T cells. In the current study, we demonstrate a novel role for KLF10 in the regulation of TGF-β receptor II (TGF-βRII) expression with functional relevance in antiviral immune response. Specifically, we show that KLF10-deficient mice have an increased number of effector/memory CD8+ T cells, display higher levels of the T helper type 1 cell-associated transcription factor T-bet, and produce more IFN-γ following in vitro stimulation. In addition, KLF10−/− CD8+ T cells show enhanced proliferation in vitro and homeostatic proliferation in vivo. Freshly isolated CD8+ T cells from the spleen of adult mice express lower levels of surface TGF-βRII (TβRII). Congruently, in vitro activation of KLF10-deficient CD8+ T cells upregulate TGF-βRII to a lesser extent compared with wild-type (WT) CD8+ T cells, which results in attenuated Smad2 phosphorylation following TGF-β1 stimulation compared with WT CD8+ T cells. Moreover, we demonstrate that KLF10 directly binds to the TGF-βRII promoter in T cells, leading to enhanced gene expression. In vivo viral infection with Daniel's strain Theiler's murine encephalomyelitis virus (TMEV) also led to lower expression of TGF-βRII among viral-specific KLF10−/− CD8+ T cells and a higher percentage of IFN-γ-producing CD8+ T cells in the spleen. Collectively, our data reveal a critical role for KLF10 in the transcriptional activation of TGF-βRII in CD8+ T cells. Thus, KLF10 regulation of TGF-βRII in this cell subset may likely play a critical role in viral and tumor immune responses for which the integrity of the TGF-β1/TGF-βRII signaling pathway is crucial.

Inducible gene expression, which requires chromatin remodeling on gene promoters, underlies the epigenetically inherited differentiation program of most immune cells. However, chromatin-mediated mechanisms that underlie these events in T regulatory cells remain to be fully characterized. Here, we report that inducibility of FOXP3, a key transcription factor for the development of T regulatory cells, depends upon Kruppel-like factor 10 (KLF10) interacting with two antagonistic histone-modifying systems. We utilized chromatin immunoprecipitation, genome-integrated reporter assays, and functional domain KLF10 mutant proteins, to characterize reciprocal interactions between this transcription factor and either the Sin3-histone deacetylase complex or the histone acetyltransferase, p300/CBP-associated factor (PCAF). We characterize a Sin3-interacting repressor domain on the NH2 terminus of KLF10, which works to limit the activating function of this transcription factor. Indeed, inactivation of this Sin3-interacting domain renders KLF10 able to physically associate with PCAF as to induce FOXP3 gene transcription. We show that this biochemical data derived from studying our genome-integrated reporter cell system are recapitulated in primary murine lymphocytes. Collectively, these results advance our understanding of how a single transcription factor, namely KLF10, functions as a toggle to integrate antagonistic signals regulating FOXP3 and, thus, immune activation.