Biology subjects

Brautigan, D. L.

Publications and source records attributed to Brautigan, D. L..

5 recordsLinked to original sources

bioRxiv2026

Hydrocephalus caused by Katnip deletion is linked to increased ciliogenesis and reduced proliferation of neuroprogenitor cells

BackgroundKATNIP (Katanin-interacting protein), also known as KIAA0556, is one of the human genes with pathogenic variants linked to Joubert syndrome, an archetypal neurodevelopmental ciliopathy. KATNIP is a scaffolding protein with a critical role in ciliogenesis. In this study, we characterized the ciliopathy phenotypes due to KATNIP gene deletion. ResultsWe produced a Katnip null mouse model using CRISPR-Cas12a (Cpf1). The null heterozygotes appeared normal while the homozygotes died around postnatal day 9, showing severe hydrocephalus and deficiency in neuroprogenitor cell proliferation. Katnip-deficient cells in the brain have a higher rate of cilia formation and longer cilia than wild type cells. ConclusionKATNIP loss of function gives rise to hydrocephalus found in Joubert syndrome. The results indicate that KATNIP restricts ciliogenesis and cilia extension and supports proliferation of neuroprogenitor cells in the brain.

cell biology↗

bioRxiv2025

Protein Phosphatase 2A Subunit B55 Alpha is Required for Angiotensin Type 2 Receptor Elicited Natriuresis

BackgroundAngiotensin type 2 receptor (AT2R) activation promotes natriuresis in renal proximal tubule cells (RPTCs) counteracting sodium retention stimulated by the AT1R. Early signaling events mediating the natriuretic response with AT2R activation in RPTCs are currently unknown. Our previous research suggested protein phosphatase 2A (PP2A) functions downstream of the AT2R. In this study, we investigated the interaction of PP2A regulatory subunit B55 with the AT2R and requirement for B55 in AT2R signaling and natriuresis. Methods and ResultsRats were subjected to renal interstitial (RI) infusion of vehicle or Compound 21 (C21), a non-peptide specific AT2R agonist, and kidney sections were probed for interactions between PP2A subunits and the AT2R using a proximity ligation assay. A dramatic 6-fold increase in AT2R-B55 interaction in apical brush border membranes of RPTCs was observed with C21 stimulation. In vitro binding of purified AT2R and B55 supported a direct interaction between these two proteins. To determine the requirement for B55 in renal AT2R signaling, siRNA targeting B55 was administered to rats in vivo by RI infusion which resulted in a [~]70% decrease in B55 in RPTCs but not distal tubules. In rats with B55 knockdown in RPTCs, natriuresis in response to C21 was abolished. Simultaneously, C21-elicited AT2R redistribution to and sodium transporter Na+/H+ exchanger-3 (NHE3) retrieval from apical brush border membranes was lost, as observed with confocal immunofluorescence microscopy. Consistent with impaired AT2R signaling, B55 knockdown prevented c-Src phosphorylation in response to C21. B55 knockdown also led to a dramatic 4 to 6-fold increase in AT2R co-localization with the lysosomal marker LAMP1, and a 50% reduction in AT2R co-localization with EEA1 and Rab 7, markers for early and late endosomes, respectively. ConclusionsPP2A B55 directly binds to the activated AT2R and is required for AT2R-elicited natriuresis, AT2R signaling and intracellular trafficking in RPTCs.

physiology↗

bioRxiv2024

An epilepsy-associated CILK1 variant compromises KATNIP regulation and impairs primary cilia and Hedgehog signaling

Mutations in human CILK1 (ciliogenesis associated kinase 1) are linked to ciliopathies and epilepsy. Homozygous point and nonsense mutations that extinguish kinase activity impair primary cilia function, whereas mutations outside the kinase domain are not well understood. Here, we produced a knock-in mouse equivalent of the human CILK1 A615T variant identified in juvenile myoclonic epilepsy (JME). This residue is in the C-terminal region of CILK1 separate from the kinase domain. Mouse embryo fibroblasts (MEF) with either heterozygous or homozygous A612T mutant alleles exhibited a higher ciliation rate, shorter individual cilia and up-regulation of ciliary Hedgehog signaling. Thus, a single A612T mutant allele was sufficient to impair primary cilia and ciliary signaling in MEFs. Gene expression profiles of wild type versus mutant MEFs revealed profound changes in cilia-related molecular functions and biological processes. CILK1 A615T mutant protein was not increased to the same level as the wild type protein when co-expressed with scaffold protein KATNIP (katanin-interacting protein). Our data show that KATNIP regulation of a JME-associated single residue variant of CILK1 is compromised and this impairs the maintenance of primary cilia and Hedgehog signaling.

cell biology↗

bioRxiv2021

Transcriptome-wide Association Study and eQTL colocalization identify potentially causal genes responsible for bone mineral density GWAS associations

Genome-wide association studies (GWASs) for bone mineral density (BMD) have identified over 1,100 associations to date. However, identifying causal genes implicated by such studies has been challenging. Recent advances in the development of transcriptome reference datasets and computational approaches such as transcriptome-wide association studies (TWASs) and expression quantitative trait loci (eQTL) colocalization have proven to be informative in identifying putatively causal genes underlying GWAS associations. Here, we used TWAS/eQTL colocalization in conjunction with transcriptomic data from the Genotype-Tissue Expression (GTEx) project to identify potentially causal genes for the largest BMD GWAS performed to date. Using this approach, we identified 512 genes as significant (Bonferroni <= 0.05) using both TWAS and eQTL colocalization. This set of genes was enriched for regulators of BMD and members of bone relevant biological processes. To investigate the significance of our findings, we selected PPP6R3, the gene with the strongest support from our analysis which was not previously implicated in the regulation of BMD, for further investigation. We observed that Ppp6r3 deletion in mice decreased BMD. In this work, we provide an updated resource of putatively causal BMD genes and demonstrate that PPP6R3 is a putatively causal BMD GWAS gene. These data increase our understanding of the genetics of BMD and provide further evidence for the utility of combined TWAS/colocalization approaches in untangling the genetics of complex traits.

genomics↗

bioRxiv2020

Phosphosite T674A mutation in kinesin family member 3A fails to reproduce tissue and ciliary defects characteristic of CILK1 loss of function

Background Kinesin family member 3A (KIF3A) is a molecular motor protein in the heterotrimeric kinesin-2 complex that drives anterograde intraflagellar transport. This process plays a pivotal role in both biogenesis and maintenance of the primary cilium that supports tissue development. Ciliogenesis associated kinase 1 (CILK1) phosphorylates human KIF3A at Thr672. CILK1 loss of function causes ciliopathies that manifest profound and multiplex developmental defects, including polydactyly, shortened and hypoplastic bones and alveoli airspace deficiency, leading to perinatal lethality. Prior studies have raised the hypothesis that CILK1 phosphorylation of KIF3A is critical for its regulation of organ development.Results We produced a mouse model with phosphorylation site Thr674 in mouse Kif3a mutated to Ala. Kif3a T674A homozygotes are viable and exhibit no skeletal abnormalities, and only mildly reduced airspace in alveoli. Mouse embryonic fibroblasts carrying Kif3a T674A mutation show a normal rate of ciliation and a moderate increase in cilia length.Conclusion These results indicate that eliminating Kif3a Thr674 phosphorylation by CILK1 is insufficient to reproduce the severe developmental defects in ciliopathies caused by Cilk1 loss of function. This suggests KIF3A phosphorylation by CILK1 is not essential for tissue development and other substrates are involved in Cilk1 ciliopathies.Competing Interest StatementThe authors have declared no competing interest.View Full Text

developmental biology↗