Mitral valve prolapse (MVP) affects 1 in 40 people and is the most common indication for mitral valve surgery. MVP can cause arrhythmias, heart failure, and sudden cardiac death, and to date, the causes of this disease are poorly understood. We now demonstrate that defects in primary cilia genes and their regulated pathways can cause MVP in familial and sporadic nonsyndromic MVP cases. Our expression studies and genetic ablation experiments confirmed a role for primary cilia in regulating ECM deposition during cardiac development. Loss of primary cilia during development resulted in progressive myxomatous degeneration and profound mitral valve pathology in the adult setting. Analysis of a large family with inherited, autosomal dominant nonsyndromic MVP identified a deleterious missense mutation in a cilia gene, DZIP1. A mouse model harboring this variant confirmed the pathogenicity of this mutation and revealed impaired ciliogenesis during development, which progressed to adult myxomatous valve disease and functional MVP. Relevance of primary cilia in common forms of MVP was tested using pathway enrichment in a large population of patients with MVP and controls from previously generated genome-wide association studies (GWAS), which confirmed the involvement of primary cilia genes in MVP. Together, our studies establish a developmental basis for MVP through altered cilia-dependent regulation of ECM and suggest that defects in primary cilia genes can be causative to disease phenotype in some patients with MVP.

Magnesium (Mg 2+ ) is abundant in plant cells and plays a critical role in many physiological processes. A 10-member gene family AtMGT (also known as AtMRS2) was identified in Arabidopsis, which belongs to a eukaryote subset of the CorA superfamily, functioning as Mg 2+ transporters. Some family members (AtMGT1 and AtMGT10) function as high-affinity Mg 2+ transporter and could complement bacterial mutant or yeast mutant lacking Mg 2+ transport capability. Here we report an AtMGT family member, AtMGT9, that functions as a low-affinity Mg 2+ transporter, and is essential for pollen development. The functional complementation assay in Salmonella mutant strain MM281 showed that AtMGT9 is capable of mediating Mg 2+ uptake in the sub-millimolar range of Mg 2+ . The AtMGT9 gene was expressed most strongly in mature anthers and was also detectable in vascular tissues of the leaves, and in young roots. Disruption of AtMGT9 gene expression resulted in abortion of half of the mature pollen grains in heterozygous mutant +/mgt9, and no homozygous mutant plant was obtained in the progeny of selfed +/mgt9 plants. Transgenic plants expressing AtMGT9 in these heterozygous plants can recover the pollen phenotype to the wild type. In addition, At-MGT9 RNAi transgenic plants also showed similar abortive pollen phenotype to mutant +/mgt9. Together, our results demonstrate that AtMGT9 functions as a low-affinity Mg 2+ transporter that plays a crucial role in male gametophyte development and male fertility.

We previously have shown that the highly conserved eight-protein exocyst trafficking complex is required for ciliogenesis in kidney tubule cells. We hypothesized here that ciliogenic programs are conserved across organs and species. To determine whether renal primary ciliogenic programs are conserved in the eye, and to characterize the function and mechanisms by which the exocyst regulates eye development in zebrafish, we focused on , a central component of the exocyst complex, by analyzing both zebrafish mutants, and photoreceptor-specific Exoc5 knock-out mice. Two separate mutant zebrafish lines phenocopied morphants and, strikingly, exhibited a virtual absence of photoreceptors, along with abnormal retinal development and cell death. Because the zebrafish mutant was a global knockout, we also observed defects in several ciliated organs, including the brain (hydrocephalus), heart (cardiac edema), and kidney (disordered and shorter cilia). knockout increased phosphorylation of the regulatory protein Mob1, consistent with Hippo pathway activation. mutant zebrafish rescue with human EXOC5 mRNA completely reversed the mutant phenotype. We accomplished photoreceptor-specific knockout of Exoc5 with our fl/fl mouse line crossed with a rhodopsin-Cre driver line. In photoreceptor-specific knock-out mice, the photoreceptor outer segment structure was severely impaired at 4 weeks of age, although a full-field electroretinogram indicated a visual response was still present. However, by 6 weeks, visual responses were eliminated. In summary, we show that ciliogenesis programs are conserved in the kidneys and eyes of zebrafish and mice and that the exocyst is necessary for photoreceptor ciliogenesis and retinal development, most likely by trafficking cilia and outer-segment proteins.

Background Bicuspid aortic valve (BAV) disease is the most common congenital heart defect affecting 0.5–1.2% of the population and causes significant morbidity and mortality. Only a few genes have been identified in pedigrees and no single gene-model explains BAV inheritance, thus supporting a complex genetic network of interacting genes. However, patients with rare syndromic diseases that stem from alterations in the structure and function of primary cilia (“ciliopathies”) exhibit BAV as a frequent cardiovascular finding, suggesting primary cilia may factor broadly in disease etiology. Results Our data are the first to demonstrate that primary cilia are expressed on aortic valve mesenchymal cells during embryonic development and are lost as these cells differentiate into collagen-secreting fibroblastic-like cells. The function of primary cilia was tested by genetically ablating the critical ciliogenic gene, Ift88. Loss of Ift88 resulted in abrogation of primary cilia and increased fibrogenic ECM production. Consequentially, stratification of ECM boundaries normally present in the aortic valve were lost and a highly penetrant BAV phenotype was evident at birth. Conclusions Our data support cilia as a novel cellular mechanism for restraining ECM production during aortic valve development and broadly implicate these structures in the etiology of BAV disease in humans.

Our objective is to assess the incidence of cardiac and intraspinal abnormities in Chinese congenital scoliosis (CS) patients and to study the relationship between the associated abnormities and the different CS types. Fivehundred and thirty-nine consecutive Chinese patients with CS were retrospectively studied, and the records of echocardiography, plain radiograph of the entire spine, magnetic resonance imaging of the entire spine and/or myelogram were reviewed. The results indicated that the incidence of cardiac and intraspinal abnormities in CS patients was 14.1 and 24.5%, respectively. There was no difference in the incidence of associated cardiac and intraspinal abnormities in different CS types (P [ 0.05). The most common cardiac abnormities in CS patients was mitral valve prolapse, which was followed by congenital heart diseases, including atrial septal defect, ventricular septal defect, bicuspid aortic valve and patent ductus ateriosus. The cardiac abnormities were not likely to be concurrent with intraspinal abnormities in CS patients (P = 0.04). The intraspinal abnormities were more common in female and older patients (all P \ 0.05). One or more abnormities mentioned above could be found in 36.8% CS patients and were more likely to be found in female patients (P \ 0.01). We concluded that CS is not a simple abnormity, due to the high incidence of associated deformities of other organs, comprehensive assessment was strongly recommended before the surgical correction for CS patients.