Comparison of Phenotypes between Different vangl2 Mutants Demonstrates Dominant Effects of the Looptail Mutation during Hair Cell Development

Abstract

Experiments utilizing the Looptail mutant mouse, which harbors a missense mutation in the vangl2 gene, have been essential for studies of planar polarity and linking the function of the core planar cell polarity proteins to other developmental signals. Originally described as having dominant phenotypic traits, the molecular interactions underlying the Looptail mutant phenotype are unclear because Vangl2 protein levels are significantly reduced or absent from mutant tissues. Here we introduce a vangl2 knockout mouse and directly compare the severity of the knockout and Looptail mutant phenotypes by intercrossing the two lines and assaying the planar polarity of inner ear hair cells. Overall the vangl2 knockout phenotype is milder than the phenotype of compound mutants carrying both the Looptail and vangl2 knockout alleles. In compound mutants a greater number of hair cells are affected and changes in the orientation of individual hair cells are greater when quantified. We further demonstrate in a heterologous cell system that the protein encoded by the Looptail mutation (Vangl2S464N) disrupts delivery of Vangl1 and Vangl2 proteins to the cell surface as a result of oligomer formation between Vangl1 and Vangl2S464N, or Vangl2 and Vangl2S464N, coupled to the intracellular retention of Vangl2S464N. As a result, Vangl1 protein is missing from the apical cell surface of vestibular hair cells in Looptail mutants, but is retained at the apical cell surface of hair cells in vangl2 knockouts. Similarly the distribution of Prickle-like2, a putative Vangl2 interacting protein, is differentially affected in the two mutant lines. In summary, we provide evidence for a direct physical interaction between Vangl1 and Vangl2 through a combination of in vitro and in vivo approaches and propose that this interaction underlies the dominant phenotypic traits associated with the Looptail mutation.

Evidence for opposing roles of Celsr3 and Vangl2 in glutamatergic synapse formation

“…Therefore, the reduction of glutamatergic synapse formation is probably secondary to these earlier defects, misrepresenting the true function of Vangl2. Furthermore, the looptail mutation has been proposed to be a gain-of-function mutation, which could lead to other unexpected artifacts (42). Therefore, our study correctly assigns the function of Celsr3 and Vangl2 in glutamatergic synapse formation, laying down the foundation for future studies in this important pathway for synapse formation and potentially plasticity.…”

“…However, Vangl2 is also an important signaling component in axon guidance. Germline Vangl2 mutations, either complete loss-of-function or gain-of-function (looptail), lead to massive axon projection defects (as well as other earlier developmental defects, such as an open neural tube), which will secondarily cause synapse formation defects (14,41,42). In two earlier studies, these germline Vangl2 mutants show a decrease in dendritic complexity and spine density (7,11).…”

Control of vertebrate core PCP protein localization and dynamics by Prickle2

“…1N). This pattern might reflect the vesicular transport proteins known to be important for the processing and trafficking of Vangl proteins (Guo et al, 2013;Merte et al, 2009;Yin et al, 2012). Both the cortical localization and asymmetry of these accumulations increased as development proceeded, with a timeframe similar to that for Dvl1 and Pk2 (Fig.…”

Frizzled 2 and frizzled 7 function redundantly in convergent extension and closure of the ventricular septum and palate: evidence for a network of interacting genes

“…we determined the frequencies of anatomical anomalies in crosses with each of the following: Vangl Lp [Lp is a semi-dominant allele (Strong and Hollander, 1949;Song, H. et al, 2010;Yin et al, 2012)], a null allele of dishevelled 3 [Dvl3; one of three highly homologous and partially redundant cytosolic signaling proteins involved in both canonical and PCP signaling (Etheridge et al, 2008)], and null alleles of Wnt3a, Wnt5a and Wnt11. Wnt3a was chosen for these experiments because there is strong in vivo evidence that it acts via the canonical pathway in the early embryo (Galceran et al, 2001;Nakaya et al, 2005).…”