Search

Rationale: Smooth muscle-motility disorders are mainly characterized by impaired contractility and functional intestinal obstruction. Some of these cases are caused by genetic mutations of smooth muscle genes ACTA2, ACTG2, MYH11, MYLK and LMOD1. Still the etiology is complex and multifactorial and the underlying pathology is poorly understood. Integrin interaction protein Kindlin-2 is widely expressed in striated and smooth muscle cells (SMC). However, the function of Kindlin-2 in the smooth muscle remains elusive. Methods: We generated two mouse models using different cre promoter transgenic mice, Kindlin-2fl/fl SM22α-cre+ (cKO mice) and Kindlin-2fl/fl; MYH-cre+ (iKO mice). Embryos and adult tissues were prepared for hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC) and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) apoptosis assay. We investigated ultrastructure changes of mouse smooth muscle using transmission electron microscopy (TEM) and measured smooth muscle contractile force in mounting aortic and intestinal rings using the multiwire myograph system (DMT 620M). In addition, cell traction force microscopy (CTFM) was applied to observe the functional change of primary SMC after Kindlin-2 depletion by RNAi. Results: Depletion of Kindlin-2 encoding gene Fermt2 in embryonic smooth muscles leads to apoptosis, downregulates the key components of SMC, impairs smooth muscle development, and finally causes embryonic death at E14.5. Tamoxifen-induced Kindlin-2-specific knockout in adult mouse smooth muscle showed decreased blood pressure, intestinal hypoperistalsis, and eventually died of intestinal obstruction. Kindlin-2 depletion also leads to downregulated Myh11, α-SMA, and CNN, shortened myofilament, broken myofibrils, and impaired contractility of the smooth muscles in iKO mice. Mechanistically, loss of Kindlin-2 decreases Ca2+ influx in primary vascular smooth muscle cells (PVSMC) by downregulating the expression of calcium-binding protein S100A14 and STIM1. Conclusion: We demonstrated that Kindlin-2 is essential for maintaining the normal structure and function of smooth muscles. Loss of Kindlin-2 impairs smooth muscle formation during embryonic development by inducing apoptosis and jeopardizes the contraction of adult smooth muscle by blocking Ca2+ influx that leads to intestinal obstruction. Mice with Kindlin-2 depletion in adult smooth muscle could be a potent animal model of intestinal obstruction for disease research, drug treatment and prognosis.

Basal-like breast cancer with a luminal progenitor gene expression profile is an aggressive subtype of breast cancer with a poorer prognosis compared with other subtypes. However, genes that specifically promote basal-like breast cancer development remain largely unknown. Here, we report that a novel gene C1orf106 plays an important role in maintaining the feature of basal-like/luminal progenitors. C1orf106 is frequently amplified and overexpressed in basal-like breast cancer and is associated with a poor outcome in patients. In human TCGA database, C1orf106 expression was correlated with upregulation of ELF5 and downregulation of GATA3, two transcription factors that regulate mammary gland stem cell fate. Enhanced expression of C1orf106 promotes tumor progression and expression of basal-like/luminal progenitor marker ELF5; depletion of C1orf106 suppresses tumorigenesis and expression of basal-like/luminal progenitor marker GATA3. These findings suggest that C1orf106 maintains the basal-like/luminal progenitor character through balancing the expression of ELF5 and GATA3. Taken together, we demonstrated that C1orf106 is an important regulator for basal-like/luminal progenitors and targeting C1orf106 is of therapeutic value for breast cancer.