A Novel PKD1 Mutation Associated With Autosomal Dominant Kidney Disease and Cerebral Cavernous Malformation

Shaping subcellular tubes through vesicle trafficking: Common and distinct pathways

Cells with subcellular lumens form some of the most miniature tubes in the tubular organs of animals. These are often crucial components of the system, executing functions at remote body locations. Unlike tubes formed by intercellular or autocellular junctions, the cells with junctionless subcellular lumens face unique challenges in modifying the cell shape and plasma membrane organization to incorporate a membrane-bound tube within, often associated with dramatic cellular growth and extensions. Results in the recent years have shown that membrane dynamics, including both the primary delivery and recycling, is crucial in providing the cell with the flexibility to face these challenges. A significant portion of this information has come from two in vivo invertebrate models; the Drosophila tracheal terminal cells and the C. elegans excretory cell. This review focuses on the data obtained from these systems in the recent past about how trafficking pathways influence subcellular tube and branching morphogenesis. Given that such tubes occur in vertebrate vasculature, these insights are relevant to human health, and we contrast our conclusions with the less understood subcellular tubes of angiogenesis.

Genetic analysis of a family presenting with coexisting cerebral cavernous malformations and polycystic kidney disease

Hereditary cerebral cavernous malformations (CCMs) are characterized by clustered dilated capillary-like vessels in the brain. Autosomal dominant polycystic kidney disease (PKD) is characterized by renal cysts and extra-renal abnormalities. We report a Taiwanese family in which the index case exhibited coexisting phenotypes of both CCMs and PKD. The index case was a 55-year-old woman with known PKD who developed an intracerebral hemorrhage (ICH) in the right medulla. Neuroimaging revealed numerous microbleeds in the bilateral cerebrum and cerebellum. Radiological CCMs were suspected given the absence of other imaging markers of small vessel disease. A comprehensive panel of 183 cerebral vascular malformation genes were investigated through genome sequencing. A novel CCM2 frameshift variant (c.607_608delCT, p.Leu203Valfs∗53) causing a pathogenic premature stop codon, and a known PKD2 nonsense variant (c.2407C > T, p.Arg803∗), were found. Segregation analysis revealed that four siblings were affected by either isolated aforementioned PKD2 or CCM2 variant. Notably, radiological CCMs were exclusively found in siblings who had this CCM2 variant, and bilateral internal carotid artery aneurysms were restricted to one sibling who had the PKD2 variant but not the CCM2 variant. Our study expands the genetic spectrum of CCM2 and demonstrates unambiguous cosegregation of CCM2 and PKD2 variants with their respective phenotypes.

Crosstalk between basal extracellular matrix adhesion and building of apical architecture during morphogenesis

Tissues build complex structures like lumens and microvilli to carry out their functions. Most of the mechanisms used to build these structures rely on cells remodelling their apical plasma membranes, which ultimately constitute the specialised compartments. In addition to apical remodelling, these shape changes also depend on the proper attachment of the basal plasma membrane to the extracellular matrix (ECM). The ECM provides cues to establish apicobasal polarity, and it also transduces forces that allow apical remodelling. However, physical crosstalk mechanisms between basal ECM attachment and the apical plasma membrane remain understudied, and the ones described so far are very diverse, which highlights the importance of identifying the general principles. Here, we review apicobasal crosstalk of two well-established models of membrane remodelling taking place during Drosophila melanogaster embryogenesis: amnioserosa cell shape oscillations during dorsal closure and subcellular tube formation in tracheal cells. We discuss how anchoring to the basal ECM affects apical architecture and the mechanisms that mediate these interactions. We analyse this knowledge under the scope of other morphogenetic processes and discuss what aspects of apicobasal crosstalk may represent widespread phenomena and which ones are used to build subsets of specialised compartments.

MiR-4787-5p regulates vascular smooth muscle cell apoptosis by targeting PKD1 and inhibiting the PI3K/Akt/FKHR pathway

ABSTRACT

Vascular smooth muscle cell (VSMC) dysfunction is the main cause of aortic dissection (AD). In this study, we focused on the role and mechanism of miR-4787-5p in regulating VSMC apoptosis. RT-qPCR was used to detect the expression of miR-4787-5p in aorta tissues of AD (n=10) and normal aortic tissues of donors (n=10). Cell apoptosis was tested by TUNEL assay and Annexin V FITC/PI staining flow cytometry. The expression of PC1 and the PI3K/Akt/FKHR signaling pathway associated proteins in VSMCs was measured by Western blot. We found that the miR-4787-5p was highly expressed in aorta tissues of AD compared with 10 healthy volunteers. Meanwhile, PI3K/Akt/FKHR signaling pathway was inactive in the aortic tissue of AD. The overexpression of miR-4787-5p significantly induced VSMC apoptosis, and miR-4787-5p knockdown showed the opposite results. In addition, polycystic kidney disease 1 gene (PKD1), which encodes polycystin-1(PC1), was found to be a direct target of miR-4787-5p in the VSMCs and this was validated using a luciferase reporter assay. Overexpression of PC1 by LV-PC1 plasmids markedly eliminated the promotion of miR-4787-5p overexpression on VSMC apoptosis. Finally, it was found that miR-4787-5p deactivated the PI3K/Akt/FKHR pathway, as demonstrated by the down-regulation of phosphorylated (p-)PI3K, p-Akt, and p-FKHR. In conclusion, these findings confirm an important role for the miR-4787-5p/PKD1 axis in AD pathobiology.

Identification of a pathogenic mutation in a Chinese pedigree with polycystic kidney disease

Polycystic kidney disease (PKD) is a life-threatening inherited disease with a morbidity of 1:500–1,000 worldwide. Numerous progressively enlarging cysts are observed in the bilateral kidneys of patients with PKD, inducing structural damage and loss of kidney function. The present study analyzed one family with PKD. Whole exome sequencing of the proband was performed to detect the pathogenic gene present in the family. Candidate gene segments for lineal consanguinity in the family were amplified by nest polymerase chain reaction, followed by Sanger sequencing. One novel duplication variant (NM_001009944.2:c.9359dupA:p.Y3120_E3121delinsX) and one missense mutation (c.G9022A:p.V3008M) were detected in PKD1. Additionally, the pathogenic substitutions in PKD1 published from the dataset were analyzed. Following analysis and confirmation, the duplication variant NM_001009944.2:c.9359dupA:p.Y3120_E3121delinsX in PKD1, within the polycystin-1, lipoxygenase, α-toxin domain, was considered to be the pathogenic factor in the examined family with autosomal dominant PKD. Additionally, based on the analysis of 4,805 pathogenic substitutions in PKD1 within various regions, the presence of the missense mutation in the N-terminal domain of polycystin-1 may present high pathogenicity in ADPKD.