Role of the Activating Transcription Factor 5a (atf5a) gene in Hair Cell Development and Regeneration

Abstract

Hair cells (HC) are sensory mechanoreceptors that are localized in sensory patches of the vertebrate inner ear. HC loss is the single leading cause of hearing and balance deficiencies. Mammals are unable to regenerate damaged HCs unlike lower vertebrates like birds, amphibians and fish. The two latter, also regenerate HCs in a superficial mechano‐sensory structure called the lateral line (LL) that allows them to sense water movements. Significant progress has been made in recent years by exploiting the experimental accessibility of the LL in a genetic tractable animal model: the zebrafish. The LL is composed of stereotypically distributed small sensory patches called neuromasts (NM). Each NM is a bulb‐shaped structure made of ~60 cells. It is externally delimited by ~10 mantle cells (MCs) which are forming an outer apical constricted ring through which protrude cilia from 12–15 centrally located HCs that are engulfed by 30–40 support cells (SC). Synchronized HC destruction will trigger a well described 3‐day regeneration program. New HCs are sequentially added from dividing and differentiating SCs. In parallel, other SCs proliferate replenishing their own stock, thus fitting the stem cell definition. Our lab has previously identified several genes with SC enriched expression. One of them is the activating transcription factor 5a (atf5a). It is a cAMP‐response element‐binding (CREB) transcription factor which was previously shown to have an important role in olfactory sensory neuron (OSN) differentiation in rodents, but was never described in the LL. To assess the role of this gene during OSN and HC development and regeneration, we first confirmed by in situ hybridization using an antisense probe directed against atf5a that it was expressed in both the olfactory pits and the LL. Next, we generated loss‐of‐function atf5a (KOs) using CRISPR‐Cas9 genome editing technology. So far, we have identified a 7 bp deletion (atf5a7D) that should represent a null allele, as reading frame shift is predicted to introduce an early stop codon in amino acid 93. We will present our preliminary results of the phenotypic analysis of homozygote (atf5a7D−/−) animals which we are focusing on the development and the regeneration of HCs in the LL and OSN in the nasal pits. Understanding the role of atf5a in the development and regeneration of these sensory tissues will help advance therapeutic regenerative approaches.Support or Funding InformationFunding: R25GM061838 MBRS‐RISE and NSF CREST Grant #HRD‐1137725This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.