Biology subjects

Fowler, B.

Publications and source records attributed to Fowler, B..

3 recordsLinked to original sources

bioRxiv2024

The MET growth signaling complex drives Alzheimers Disease-associated brain pathology in aged Shugoshin 1 mouse cohesinopathy model

The understanding on molecular processes toward Late-onset Alzheimers Disease (LOAD) has been insufficient to design LOAD intervention drugs. Previously, we discovered transgenic genomic instability model mice Sgo1-/+ accumulate cerebral amyloid-beta in old age. We proposed the "amyloid-beta accumulation cycle" hypothesis, in which cytotoxic, mitogenic and aneuploidgenic amyloid can create an autonomous mitotic cycle leading to accumulation of itself. However, the nature of the growth signaling that drives cells toward pathogenic mitotic cycle remained unidentified. In this study, we hypothesized that the aged Sgo1-/+ mice brains would show signs of mitogenic signaling activation, and searched for growth signaling activated in the vicinity of amyloid-beta, with spatial analysis on the cortex and hippocampus of Sgo1-/+ mice in middle-age and old-age. The analysis indicated activations of kinase signaling p42/44 MAPK ERK1/2, AMPK, JNK, Wnt signaling via GSK3 inactivation, as well as increases of p-TAU and other AD biomarkers, PLCG1, EGFR, MET, Neurofibromin and RAS. Immune activation markers CD45 and CD31 were also elevated in the microenvironment. A majority of activated growth signaling components are of the oncogenic MET signaling complex. The discovery supports repurposing of cancer drugs targeting the MET signaling complex and EGFR-RAS-MAPK axis for intervention and/or treatment of genomic instability-driven AD.

neuroscience↗

bioRxiv2020

Biallelic mutation of CLRN2 causes non-syndromic hearing loss in humans

Deafness, the most frequent sensory deficit in humans, is extremely heterogenous with hundreds of genes probably involved. Clinical and genetic analyses of an extended consanguineous family with pre-lingual, moderate-to-profound autosomal recessive sensorineural hearing loss, allowed us to identify CLRN2, encoding a tetraspan protein as a new deafness gene. Homozygosity mapping followed by exome sequencing identified a 15.2 Mb locus on chromosome 4p15.32p15.1 containing a missense pathogenic variant in CLRN2 (c.494C>A, NM_001079827.2) segregating with the disease. Using in vitro RNA splicing analysis, we show that the CLRN2 c.494C>A mutation leads to two events: 1) the substitution of a highly conserved threonine (uncharged amino acid) to lysine (charged amino acid) at position 165, p.(Thr165Lys), and 2) aberrant splicing, with the retention of intron 2 resulting in a stop codon after 26 additional amino acids, p.(Gly146Lysfs*26). Expression studies and phenotyping of newly produced zebrafish and mouse models deficient for clarin 2 further confirm that clarin 2, expressed in the inner ear hair cells, is essential for normal organization and maintenance of the auditory hair bundles, and for hearing function. Together, our findings identify CLRN2 as a new deafness gene, which will impact future diagnosis and treatment for deaf patients.

genetics↗

bioRxiv2018

Genetic, structural, and functional analysis of mutations causing methylmalonyl-CoA epimerase deficiency

Human methylmalonyl-CoA epimerase (MCEE) catalyzes the interconversion of D-methylmalonyl-CoA and L-methylmalonyl-CoA in propionate catabolism. Autosomal recessive mutations in MCEE reportedly cause methylmalonic aciduria (MMAuria) in eleven patients. We investigated a cohort of 150 individuals suffering from MMAuria of unknown origin, identifying ten new patients with mutations in MCEE. Nine patients were homozygous for the known nonsense mutation p.Arg47* (c.139C>T), and one for the novel missense mutation p.Ile53Arg (c.158T>G). To understand better the molecular basis of MCEE deficiency, we mapped p.Ile53Arg, and two previously described patient mutations p.Lys60Gln and p.Arg143Cys, onto our 1.8 [A] structure of wild-type (wt) human MCEE. This revealed potential dimeric assembly disruption by p.Ile53Arg, but no clear defects from p.Lys60Gln or p.Arg143Cys. Functional analysis of MCEE-Ile53Arg expressed in a bacterial recombinant system as well as patient-derived fibroblasts revealed nearly undetectable soluble protein levels, defective globular protein behavior, and using a newly developed assay, lack of enzymatic activity - consistent with misfolded protein. By contrast, soluble protein levels, unfolding characteristics and activity of MCEE-Lys60Gln were comparable to wt, leaving unclear how this mutation may cause disease. MCEE-Arg143Cys was detectable at comparable levels to wt MCEE, but had slightly altered unfolding kinetics and greatly reduced activity. We solved the structure of MCEE-Arg143Cys to 1.9 [A] and found significant disruption of two important loop structures, potentially impacting surface features as well as the active-site pocket. These studies reveal ten new patients with MCEE deficiency and rationalize misfolding and loss of activity as molecular defects in MCEE-type MMAuria.

biochemistry↗