rodent-kidney-explant-culture-establishment-primary-ureteric-bud

Rodent Kidney Explant Culture and Establishment of Primary Ureteric Bud Epithelial Cell Culture

The developing kidney is a widely used model system to study mammalian organogenesis. Renal differentiation is orchestrated by reciprocal inductive tissue ...

University of Helsinki

Branching morphogenesis orchestrates organogenesis in many tissues, including the kidney, where ureteric bud (UB) branching determines kidney size and shape and the final nephron number. Molecular regulation of UB branching is rather well studied, whereas the cellular mechanisms and tissue organization during UB arborization are less understood. Here, we characterized epithelial cell morphology in three dimensions (3D), studied mechanisms regulating cell shape changes, and analyzed their contribution to novel branch initiation in normal and branching-incompetent bud tips. Unbiased machine-learning-based segmentation of tip epithelia identified geometrical round-to-elliptical transformation as a key cellular mechanism facilitating growth direction changes to gain optimal branching complexity. Cell shape and molecular analyses in branching-incompetent epithelia demonstrated a distinct failure to condense cell size and modify its conformation. This, together with changes in adhesive forces, defective actin dynamics, and disorganization in myosin-9 (MYH9)-based microtubules, suggests altered biophysical properties in tip cells, where branch point decisions are made and actualized. The data demonstrate that dynamic changes in volume and morphology of individual epithelial cells, together with optimal traction stress, facilitate novel branch formation in the UB tip niche. Based on these results, we propose a model where epithelial cell crowding, in tandem with stretching, transforms individual cells into elliptical and elongated shapes. This creates local curvatures that drive new branch formation during the ampulla-to-asymmetric ampulla transition of the UB.

Epithelial cell shape changes contribute to regulation of ureteric bud branching morphogenesis.

The mRNA export factor GLE1 protein plays critical yet enigmatic functions in RNA processing and has been linked with multiple developmental disorders, including lethal congenital contracture syndrome 1 (LCCS1). Using in vivo genetic engineering to study disturbed GLE1 functions under physiological conditions, we demonstrate that total inactivation of GLE1 results in disorganization of the blastocyst inner cell mass and early embryonic lethality due to defects in lineage specification. In contrast, the knock-in mice genocopying the LCCS1-associated GLE1 variant (Gle1) survive the prenatal period but die suddenly at midadulthood. Gle1 mice present an irregular count and distribution of spinal motor neurons as well as impaired development of neural crest-derived tissues, as demonstrated by defects in the sympathetic innervation of heart ventricles, irregularities in the paravertebral sympathetic ganglia volume, and decreased adrenal chromaffin cell counts. Unlike previously reported for yeast and HeLa cells, analysis of the molecular consequences of the GLE1 variant identified normal poly(A) + RNA distribution in Gle1 cells; however, cells were impaired in RNA and protein synthesis and simultaneously showed severely disturbed formation of G3BP stress granule assembly factor 1 (G3BP1)-positive stress granules. Intriguingly, stressed Gle1 cells show microRNA profiles indicative of impaired transcription, protein metabolism, nervous system development, and axon guidance, further corroborating our functional findings. Our results show the necessity of functional GLE1 for life and indicate that LCCS1 etiology is a result of the pathogenic GLE1 variant impinging differentiation of neural crest derivatives and leading to complex multiorgan defects.

Article	Year
Epithelial cell shape changes contribute to regulation of ureteric bud branching morphogenesis. The FEBS journal\| PubMed ID: 40517306	2025
In vivo modeling of lethal congenital contracture syndrome 1 suggests pathomechanisms in cellular stress responses. The FEBS journal\| PubMed ID: 40674274	2025

Julia Koivula

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