DAAM2 Variants Cause Nephrotic Syndrome via Actin Dysregulation.

The discovery of >60 monogenic causes of nephrotic syndrome (NS) has revealed a central role for the actin regulators RhoA/Rac1/Cdc42 and their effectors, including the formin INF2. By whole-exome sequencing (WES), we here discovered bi-allelic variants in the formin DAAM2 in four unrelated families with steroid-resistant NS. We show that DAAM2 localizes to the cytoplasm in podocytes and in kidney sections. Further, the variants impair DAAM2-dependent actin remodeling processes: wild-type DAAM2 cDNA, but not cDNA representing missense variants found in individuals with NS, rescued reduced podocyte migration rate (PMR) and restored reduced filopodia formation in shRNA-induced DAAM2-knockdown podocytes. Filopodia restoration was also induced by the formin-activating molecule IMM-01. DAAM2 also co-localizes and co-immunoprecipitates with INF2, which is intriguing since variants in both formins cause NS. Using in vitro bulk and TIRF microscopy assays, we find that DAAM2 variants alter actin assembly activities of the formin. In a Xenopus daam2-CRISPR knockout model, we demonstrate actin dysregulation in vivo and glomerular maldevelopment that is rescued by WT-DAAM2 mRNA. We conclude that DAAM2 variants are a likely cause of monogenic human SRNS due to actin dysregulation in podocytes. Further, we provide evidence that DAAM2-associated SRNS may be amenable to treatment using actin regulating compounds.

Prioritization of Monogenic Congenital Anomalies of the Kidney and Urinary Tract Candidate Genes with Existing Single-Cell Transcriptomics Data of the Human Fetal Kidney.

INTRODUCTION: Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in the first 3 decades of life. Over 40 genes have been identified as causative for isolated human CAKUT. However, many genes remain unknown, and the prioritization of potential CAKUT candidate genes is challenging. To develop an independent approach to prioritize CAKUT candidate genes, we hypothesized that monogenic CAKUT genes are most likely co-expressed along a temporal axis during kidney development and that genes with coinciding high expression may represent strong novel CAKUT candidate genes. METHODS: We analyzed single-cell mRNA (sc-mRNA) transcriptomics data of human fetal kidney for temporal sc-mRNA co-expression of 40 known CAKUT genes. A maximum of high expression in consecutive timepoints of kidney development was found for four of the 40 genes (EYA1, SIX1, SIX2, and ITGA8) in nephron progenitor cells a, b, c, d (NPCa-d). We concluded that NPCa-d are relevant for CAKUT pathogenesis and intersected two lists of CAKUT candidate genes resulting from unbiased whole-exome sequencing (WES) with the 100 highest expressed genes in NPCa-d. RESULTS: Intersection of the 100 highest expressed genes in NPCa-d with WES-derived CAKUT candidate genes identified an overlap with the candidate genes KIF19, TRIM36, USP35, CHTF18, in each of which a biallelic variant was detected in different families with CAKUT. CONCLUSION: Sc-mRNA expression data of human fetal kidney can be utilized to prioritize WES-derived CAKUT candidate genes. KIF19, TRIM36, USP35, and CHTF18 may represent strong novel candidate genes for CAKUT.

Studies on acceptance, evaluation and impact of the Cologne program "Research and Medical Studies".

Introduction: The curricular implementation of events (or programs) for science-related training in human medicine has been on the agenda of the medical faculties since the publication of the Federal-State Working Group [1]. The Medical Faculty of the University of Cologne developed and established a systematic, longitudinal science curriculum together with the start of the model curriculum in human medicine in 2003. Here, we investigate the questions of whether the described (para-) curricular elements are accepted by students and lecturers and how they are evaluated, especially by students. In addition, we investigate whether selected parameters can be used to demonstrate changes in the students' scientific activities. Project description: The program "Research and Medical Studies" (RaMS) consists of several components: these elements of the mandatory curricular (Scientific Projects, SP) and optional components (Research in Medical Studies (RiMS), Research Track (RT), Research Fair Cologne (RFC)) are described here. Results were recorded at various levels: Likert Scale evaluation of the event's elements were collected as satisfaction parameters from the studentsProcess data on participation in the voluntary events were collected and evaluated as absolute and relational figures (WS 12/13-SS 17). Data on the outcome of the RaMS program were collected: Type of scientific projects in the academic years 2011/12-2014/15), number and type of available projects offered at the RFC (in the years 2011-18) and number of student research funding applications in a comparison of the periods 2010-13 vs. 2014-17). Results: The students' acceptance of mandatory and paracurricular courses of the RaMS program is pleasingly high, which is not surprising, at least in the case of the voluntary courses. The participation of students in RiMS, RT and RFC is satisfactory for voluntary courses. In the case of the RT, with certified participation of approximately 47% of all registrations (corresponding to 10% of the total cohort), this is comparable to similar programs. It can be shown that the number of experimental science projects has more than doubled over time in parallel with the development of RaMS. The average number of provided projects according to the RFC is 42 (which corresponds to a placement rate of approx. 1:4). The number of successful student applications for a research support grant during the period the measures were implemented has doubled. Discussion and conclusion: The RaMS program shows a route for the implementation of the SP required by the next licensing regulations in medical education, which was initially supported and expanded solitarily, later by further elements (RiMS), also in the sense of a science-based career development (RT, RFC). The student acceptance and the measured success, in the form of successful participation in the Research Track, increased choice of experimental projects, significant increase of submitted as well as approved research grants and the high project placement rate of the Research Fair, encourage the further development of the program, which is indicated in the conclusion.