RhoE Deficiency Produces Postnatal Lethality, Profound Motor Deficits and Neurodevelopmental Delay in Mice

Abstract

Rnd proteins are a subfamily of Rho GTPases involved in the control of actin cytoskeleton dynamics and other cell functions such as motility, proliferation and survival. Unlike other members of the Rho family, Rnd proteins lack GTPase activity and therefore remain constitutively active. We have recently described that RhoE/Rnd3 is expressed in the Central Nervous System and that it has a role in promoting neurite formation. Despite their possible relevance during development, the role of Rnd proteins in vivo is not known. To get insight into the in vivo function of RhoE we have generated mice lacking RhoE expression by an exon trapping cassette. RhoE null mice (RhoE gt/gt) are smaller at birth, display growth retardation and early postnatal death since only half of RhoE gt/gt mice survive beyond postnatal day (PD) 15 and 100% are dead by PD 29. RhoE gt/gt mice show an abnormal body position with profound motor impairment and impaired performance in most neurobehavioral tests. Null mutant mice are hypoactive, show an immature locomotor pattern and display a significant delay in the appearance of the hindlimb mature responses. Moreover, they perform worse than the control littermates in the wire suspension, vertical climbing and clinging, righting reflex and negative geotaxis tests. Also, RhoE ablation results in a delay of neuromuscular maturation and in a reduction in the number of spinal motor neurons. Finally, RhoE gt/gt mice lack the common peroneal nerve and, consequently, show a complete atrophy of the target muscles. This is the first model to study the in vivo functions of a member of the Rnd subfamily of proteins, revealing the important role of Rnd3/RhoE in the normal development and suggesting the possible involvement of this protein in neurological disorders.

The Knockout of Secretin in Cerebellar Purkinje Cells Impairs Mouse Motor Coordination and Motor Learning

“…This difference was replicated using a second cohort of mice (Figures 4b and c; medium ¼ P7 vs P6 in righting and P9 vs P7 in negative geotaxis; po0.001 using non-parametric K-S test). Both reflexes have previously been used to evaluate cerebellar development (Mocholi et al, 2011;Yu et al, 2008). Our data therefore suggest that SCT knockout in Purkinje cells can lead to neural developmental delays in the cerebellum.…”

“…The wire hanging test was performed using previously reported procedures (Mocholi et al, 2011;Paylor et al, 1998). In brief, a metal wire mesh (0.5 mm diameter, 5 mm wide grid) was fixed horizontally 30 cm above the table.…”

“…Two cerebellar neuron reflexes were tested: (1) righting reflex. The juvenile animal was put down on its back, and the positive reflex was identified as the ability to turn the body upright within 30 s (Mocholi et al, 2011;Yu et al, 2008). (2) Negative geotaxis reflex.…”

“…The mouse was put on a 451 inclined plane with its head facing downwards. Mice that could turn around and crawl up the slope were considered as having the positive reflex (Mocholi et al, 2011).…”

Rnd3 as a Novel Target to Ameliorate Microvascular Leakage

“…Using a combination of cell culture, ex vivo, and in vivo approaches, we have identified evidence supporting that Rnd3 has barrier‐protective properties under certain conditions, such as following acute inflammatory challenge. The involvement of Rnd3 in the control of endothelial barrier function adds to a growing list of recently described functions ascribed to Rnd family proteins, including Ca 2+ homeostasis in the heart,53 regulation of Notch1 signaling,54 control of cell cycle progression,55, 56, 57 development of the central nervous system,58, 59, 60 control of cell motility and metastatic potential of certain cancers,29, 61, 62, 63, 64 and a potential role in cardioprotection against heart failure 65. In addition, we provide novel evidence that delivery of Rnd3 protein can serve as a potential therapeutic tool to ameliorate microvascular hyperpermeability caused by tissue injury.…”