Biology subjects

Martin, J. E.

Publications and source records attributed to Martin, J. E..

3 recordsLinked to original sources

bioRxiv2023

Failed reprogramming of transformed cells due to induction of apoptosis and senescence impairs tumor progression in lung cancer

Cell reprogramming to pluripotency applied to the study of cancer has identified transformation and pluripotency as two independent and incompatible cell fates. A detailed knowledge of the relationship between transformation and reprogramming could lead to the identification of new vulnerabilities and therapeutic targets in cancer. Here, we explore this interplay and find that OSKM expression limits tumor cell growth by inducing apoptosis and senescence. We identify Oct4 and Klf4 as the main individual reprogramming factors responsible for this effect. Mechanistically, the induction of cell cycle inhibitor p21 downstream of the reprogramming factors acts as mediator of cell death and senescence. Using a variety of in vivo systems, including allografts, orthotopic transplantation and KRAS-driven lung cancer mouse models, we demonstrate that OSKM expression impairs tumor growth and reduces tumor burden.

cell biology↗

bioRxiv2020

Species differences in the cerebellar distribution of six members of the Kv1 channel subfamily.

Comprehensive studies on the distribution of the Kv1 subfamily have been performed in rat (Chung et al., 2001) and gerbil (Chung et al., 2005), but not in mouse or human. We hypothesized that species differences may exist in the localization of these proteins. Two sets of polyclonal antibodies to Kv1.1-6 were used. Immunohistochemistry was performed on archived, formalin-fixed tissue from disease-free human, monkey and mouse cerebellum. Mouse staining corresponded to that described in rat and gerbil, with strong Kv1.1 and Kv1.2 immunoreactivities in the basket cell pinceau at the base of Purkinje cells. Kv1.3, Kv1.4, Kv1.5 and Kv1.6 were predominantly expressed in Purkinje cells. Human and monkey samples showed a similar pattern to mouse for Kv1.1, Kv1.2, Kv1.3 and Kv1.5. However, little or no Purkinje cell staining was seen in the primates with Kv1.4 and Kv1.6, and strong stellate cell expression was noted. All staining was abolished by cognate peptide blocking. Similar distributions were seen with both sets of antibodies. We conclude that there are marked species differences in the distribution of Kv1.4 and Kv1.6 between primates and rodents. Choosing appropriate animal models for studying physiological and disease processes may prove vital for translating research outcomes into clinical applications.

neuroscience↗

bioRxiv2020

Patient-specific Alzheimer-like pathology in trisomy 21 cerebral organoids reveals BACE2 as a gene-dose-sensitive AD-suppressor in human brain

A population of >6 million people worldwide at high risk of Alzheimers disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of {beta}-amyloid-(A{beta})-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar A{beta} deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome-21-gene BACE2, but prevented by combined chemical {beta} and {gamma}-secretase inhibition. We found that T21-organoids secrete increased proportions of A{beta}-preventing (A{beta}1-19) and A{beta}-degradation products (A{beta}1-20 and A{beta}1-34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1-inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in [~]30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.

neuroscience↗