Lack of WWC2 Protein Leads to Aberrant Angiogenesis in Postnatal Mice

WWC2 modulates GABAA-receptor-mediated synaptic transmission, revealing class-specific mechanisms of synapse regulation by WWC family proteins

The WW and C2 domain-containing protein (WWC2) is implicated in several neurological disorders. Here, we demonstrate that WWC2 interacts with inhibitory, but not excitatory, postsynaptic scaffolds, consistent with prior proteomic identification of WWC2 as a putative component of the inhibitory postsynaptic density. Using mice lacking WWC2 expression in excitatory forebrain neurons, we show that WWC2 suppresses γ-aminobutyric acid type-A receptor (GABAAR) incorporation into the plasma membrane and regulates HAP1 and GRIP1, which form a complex promoting GABAAR recycling to the membrane. Inhibitory synaptic transmission is increased in CA1 pyramidal cells lacking WWC2. Furthermore, unlike the WWC2 homolog KIBRA (kidney/brain protein; WWC1), a key regulator of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) trafficking at excitatory synapses, the deletion of WWC2 does not affect synaptic AMPAR expression. In contrast, loss of KIBRA does not affect GABAAR membrane expression. These data reveal synapse class-selective functions for WWC proteins as regulators of ionotropic neurotransmitter receptors and provide insight into mechanisms regulating GABAAR membrane expression.

Modulation of GABA A receptor trafficking by WWC2 reveals class-specific mechanisms of synapse regulation by WWC family proteins

WWC2 (WW and C2 domain-containing protein) is implicated in several neurological disorders, however its function in the brain has yet to be determined. Here, we demonstrate that WWC2 interacts with inhibitory but not excitatory postsynaptic scaffolds, consistent with prior proteomic identification of WWC2 as a putative component of the inhibitory postsynaptic density. Using mice lacking WWC2 expression in excitatory forebrain neurons, we show that WWC2 suppresses GABA A R incorporation into the plasma membrane and regulates HAP1 and GRIP1, which form a complex promoting GABA A R recycling to the membrane. Inhibitory synaptic transmission is dysregulated in CA1 pyramidal cells lacking WWC2. Furthermore, unlike the WWC2 homolog KIBRA (WWC1), a key regulator of AMPA receptor trafficking at excitatory synapses, deletion of WWC2 does not affect synaptic AMPAR expression. In contrast, loss of KIBRA does not affect GABA A R membrane expression. These data reveal unique, synapse class-selective functions for WWC proteins as regulators of ionotropic neurotransmitter receptors and provide insight into mechanisms regulating GABA A R membrane expression.

WWC2 expression in the testis: Implications for spermatogenesis and male fertility

The family of WWC proteins is known to regulate cell proliferation and organ growth control via the Hippo signaling pathway. As WWC proteins share a similar domain structure and a common set of interacting proteins, they are supposed to fulfill compensatory functions in cells and tissues. While all three WWC family members WWC1, WWC2, and WWC3 are found co-expressed in most human organs including lung, brain, kidney, and liver, in the testis only WWC2 displays a relatively high expression. In this study, we investigated the testicular WWC2 expression in spermatogenesis and male fertility. We show that the Wwc2 mRNA expression level in mouse testes is increased during development in parallel with germ cell proliferation and differentiation. The cellular expression of each individual WWC family member was evaluated in published single-cell mRNA datasets of murine and human testes demonstrating a high WWC2 expression predominantly in early spermatocytes. In line with this, immunohistochemistry revealed cytosolic WWC2 protein expression in primary spermatocytes from human testes displaying full spermatogenesis. In accordance with these findings, markedly lower WWC2 expression levels were detected in testicular tissues from mice and men lacking germ cells. Finally, analysis of whole-exome sequencing data of male patients affected by infertility and unexplained severe spermatogenic failure revealed several heterozygous, rare WWC2 gene variants with a proposed damaging function and putative impact on WWC2 protein structure. Taken together, our findings provide novel insights into the testicular expression of WWC2 and show its cell-specific expression in spermatocytes. As rare WWC2 variants were identified in the background of disturbed spermatogenesis, WWC2 may be a novel candidate gene for male infertility.

Distinctive Roles of YAP and TAZ in Human Endothelial Progenitor Cells Growth and Functions

The hippo signaling pathway plays an essential role in controlling organ size and balancing tissue homeostasis. Its two main effectors, yes-associated protein (YAP) and WW domain-containing transcription regulator 1, WWTR1 or TAZ, have also been shown to regulate endothelial cell functions and angiogenesis. In this study, the functions of YAP and TAZ in human endothelial progenitor cells (EPCs) were investigated by a loss-of-function study using CRISPR/Cas9-mediated gene knockdown (KD). Depletion of either YAP or TAZ reduced EPC survival and impaired many of their critical functions, including migration, invasion, vessel-formation, and expression of pro-angiogenic genes. Notably, TAZ-KD EPCs exhibited more severe phenotypes in comparison to YAP-KD EPCs. Moreover, the conditioned medium derived from TAZ-KD EPCs reduced the survivability of human lung cancer cells and increased their sensitivity to chemotherapeutic agents. The overexpression of either wild-type or constitutively active TAZ rescued the impaired phenotypes of TAZ-KD EPCs and restored the expression of pro-angiogenic genes in those EPCs. In summary, we demonstrate the crucial role of Hippo signaling components, YAP and TAZ, in controlling several aspects of EPC functions that can potentially be used as a drug target to enhance EPC functions in patients.