KLF13 is a genetic modifier of the Holt-Oram syndrome gene TBX5

Abstract

TBX5, a member of the T-box family of transcription factors, is a dosage sensitive regulator of heart development. Mutations in TBX5 are responsible for Holt-Oram Syndrome, an autosomal dominant disease with variable and partially penetrant cardiac defects suggestive of the existence of genetic and environmental modifiers. KLF13, a member of the Krüppel-like family of zinc finger proteins is co-expressed with TBX5 in several cardiac cells including atrial cardiomyocytes and cells of the interatrial septum. We report that KLF13 interacts physically and functionally with TBX5 to synergistically activate transcription of cardiac genes. We show that TBX5 contacts KLF13 via its T-domain and find that several disease-causing mutations therein have decreased KLF13 interaction. Whereas Klf13 heterozygote mice have no detectable cardiac defects, loss of a Klf13 allele in Tbx5 heterozygote mice significantly increases the penetrance of TBX5-dependent cardiac abnormalities including atrial, atrial-ventricular and ventricular septal defects. The results reveal for the first time combinatorial interaction between a T-box protein and a KLF family member and its importance for heart and possibly other organ development. The data also suggest that, in human, KLF13 may be a genetic modifier of the Holt-Oram Syndrome gene TBX5.

Identification and analysis of KLF13 variants in patients with congenital heart disease

“…Previously, we showed that KLF13 and TBX5 exhibit physical and functional interactions and that a combined heterozygous loss of TBX5 and its associated KLF13 leads to decreased postnatal viability and a higher incidence of septal defects compared to that of Tbx5 heterozygous mice. Additionally, several TBX5 mutations have been associated with CHDs, as indicated by impaired functional and physical interactions with KLF13, which confirms that TBX5 is a genetic cofactor of KLF13 [9]. In the present study, the increased transcriptional activity of BNP was more pronounced when wild-type KLF13 was cotransfected with TBX5, which indicated that KLF13 has functional interactions with TBX5 to activate BNP promoters.…”

“…In the present study, the increased transcriptional activity of BNP was more pronounced when wild-type KLF13 was cotransfected with TBX5, which indicated that KLF13 has functional interactions with TBX5 to activate BNP promoters. In our previous study of the structure-function of TBX5-KLF13 synergy [9], the N-terminal domain of KLF13 was mainly found to support synergy with TBX5. The two variants of KLF13 that were detected in the 309 CHD patients were in the N-terminal domain of the protein.…”

“…Previously, we reported that KLF13 is a TBX5 cofactor; these two proteins were found to colocalize in several cardiac cells, and they physically and functionally interact to synergistically activate cardiac promoters [9]. Therefore, to verify the impact of KLF13 variants on physical interactions with TBX5, wild-type or variant KLF13 constructs were cotransfected with TBX5 using the BNP-luciferase reporter.…”

“…Kruppel-like factor 13 (KLF13) protein has been identified as a novel collaborator of the cardiac GATA4 and TBX5 factors, which are highly expressed in the endocardium and myocardium during embryonic development. Knocking down KLF13 alleles in Xenopus embryos leads to valve immaturity, septal defects, and hypotrabeculation [7][8][9]. However, the mechanisms of KLF13 dysfunction causing CHDs are still poorly understood.…”

“…TBX5 cooperates with other transcription factors, such as GATA4 and NKX2.5, to synergistically regulate downstream targets during cardiac development [ [15,16]]. Previously, we showed that KLF13 is a TBX5 cofactor and that KLF13 may be a genetic modifier of Holt-Oram Syndrome and possibly other congenital heart diseases [9].…”