The murine ortholog of Kaufman oculocerebrofacial syndrome protein Ube3b regulates synapse number by ubiquitinating Ppp3cc

Abstract

Kaufman oculocerebrofacial syndrome (KOS) is a severe autosomal recessive disorder characterized by intellectual disability, developmental delays, microcephaly and characteristic dysmorphisms. Biallelic mutations of UBE3B, encoding for a ubiquitin ligase E3B are causative for KOS. In this report, we characterize neuronal functions of its murine ortholog Ube3b. We show that Ube3b regulates dendritic branching in a cell-autonomous manner.Moreover, Ube3b knockout (KO) neurons exhibit increased density and aberrant morphology of dendritic spines, altered synaptic physiology and changes in hippocampal circuit activity. Dorsal forebrain-specific Ube3b KO animals show impaired spatial learning and alterations in social interactions. We further demonstrate that Ube3b ubiquitinates the catalytic γ-subunit of calcineurin (Ppp3cc), the overexpression of which phenocopies the loss of Ube3b with regard to dendritic spine density. This work provides insights into the molecular pathologies underlying intellectual disability-like phenotypes in a genetic mouse model for KOS.

Case Report: A Novel PAX3 Mutation Associated With Waardenburg Syndrome Type 1

“…Splice variants frequently give rise to alternative splicing and affect protein coding. Consistent with the results, the mutations identified in Ehlers-Danlos-syndrome-related gene COL5A1 (Tuna et al, 2019;Angwin et al, 2020) and Kaufman-Oculocerebrofacial-syndrome-related gene UBE3B (Cheon et al, 2019;Ambrozkiewicz et al, 2020) also had a higher risk of disease. However, no results of the PAX3 mutation were available through the prediction tools.…”

Ire1α-Regulated mRNA Translation Rate Controls the Identity and Polarity of Upper Layer Cortical Neurons

“…Destination vectors were linearized with EcoRI-HF (New England BioLabs). pRai-HA-IRE1α Human IRE1α cDNA (NM_001433.3) was amplified from plasmid template (Addgene, #13009) using the following oligos: 5'-agattacgctatctgtacaggcATGCCGGCCCGGCGGCTG-3' and 5'-ggccgctagcccgggtaccgCTTGGTTTGGGAAGCCTGGTCTCCCTGC-3' and inserted into the modified pRaichu vector (Ambrozkiewicz et al, 2020). pCAGIG-6XHis-eEF2 Murine eEF2 cDNA (NM_007907.2) was amplified from cDNA library using the following oligos: 5'-gtctcatcattttggcaaagATGCATCATCATCATCATCATGTGAACTTCACAGTAGATC-3' and 5'-cggccgcgatatcctcgaggCTACAGTTTGTCCAGGAAGTTG-3' and inserted into pCAGIG vector for simultaneous expression of 6XHis-tagged eEF2 and EGFP.…”

Molecular Evolution, Neurodevelopmental Roles and Clinical Significance of HECT-Type UBE3 E3 Ubiquitin Ligases

“…Regarding the HECT ligases, these are the function of the catalytic HECT domain and do not seem to depend on the E2 conjugating enzyme, but rather are located within the 60 amino acids of the C-terminus of the HECT domain C-lobe [ 25 ]. Within the HECT family, UBE3A preferentially forms K48 polyUb chain [ 25 ], Ube3b is able to form both K48- and K63-linked chain [ 26 ] and UBE3C catalyzes K48- and less preponderant K29- and K11-linked chains [ 27 ]. K29 chains exist in cells within heterotypic and branched polyUb chains, among other Ub species [ 28 ].…”

“…Theoretical modeling of Q727P substitution predicts it renders the HECT domain unfit for substrate binding and positioning towards catalytic cysteine, required for efficient ubiquitination [ 36 ]. HECT-localized KOS-linked substitutions G779R and R997P fail to restore deficient dendritic arbors of Ube3b conditional forebrain-specific knockout (cKO) neurons, and the latter one exhibits altered subneuronal localization, when compared to the native UBE3B [ 26 ]. It is possible, that perinuclear localization of R997P UBE3B represents its ER-trapped folding-deficient form, similar to the case of another postsynapse-associated ASD-linked protein, neuroligin-4 [ 37 ].…”

“…Moreover, Ube3b cKO male mice exhibit a behavioral switch towards self-directed actions (like grooming and eating) at the expense of exteroceptive behaviors, such as exploration. On a molecular level, with regard to its synaptogenic function, Ube3b ubiquitinates γ-subunit of calcineurin, Ppp3cc and regulates its levels at the synapse [ 26 ]. Among the putative UBE3B interactors identified by affinity chromatography were regulatory subunits of protein phosphatases, as well [ 106 ].…”