AUTHOR=Kurtova Anastasia I. , Finoshin Alexander D. , Aparina Margarita S. , Gazizova Guzel R. , Kozlova Olga S. , Voronova Svetlana N. , Shagimardanova Elena I. , Ivashkin Evgeny G. , Voronezhskaya Elena E. 

TITLE=Expanded expression of pro-neurogenic factor SoxB1 during larval development of gastropod Lymnaea stagnalis suggests preadaptation to prolonged neurogenesis in Mollusca

JOURNAL=Frontiers in Neuroscience

VOLUME=18

YEAR=2024

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2024.1346610

DOI=10.3389/fnins.2024.1346610

ISSN=1662-453X

ABSTRACT=<sec id="sec1001"><title>Introduction</title><p>The remarkable diversity observed in the structure and development of the molluscan nervous system raises intriguing questions regarding the molecular mechanisms underlying neurogenesis in <italic>Mollusca</italic>. The expression of SoxB family transcription factors plays a pivotal role in neuronal development, thereby offering valuable insights into the strategies of neurogenesis.</p></sec><sec id="sec2001"><title>Methods</title><p>In this study, we conducted gene expression analysis focusing on SoxB-family transcription factors during early neurogenesis in the gastropod <italic>Lymnaea stagnalis</italic>. We employed a combination of hybridization chain reaction in situ hybridization (HCR-ISH), immunocytochemistry, confocal microscopy, and cell proliferation assays to investigate the spatial and temporal expression patterns of <italic>LsSoxB1</italic> and <italic>LsSoxB2</italic> from the gastrula stage to hatching, with particular attention to the formation of central ring ganglia.</p></sec><sec id="sec3001"><title>Results</title><p>Our investigation reveals that <italic>LsSoxB1</italic> demonstrates expanded ectodermal expression from the gastrula to the hatching stage, whereas expression of <italic>LsSoxB2</italic> in the ectoderm ceases by the veliger stage. <italic>LsSoxB1</italic> is expressed in the ectoderm of the head, foot, and visceral complex, as well as in forming ganglia and sensory cells. Conversely, <italic>LsSoxB2</italic> is mostly restricted to the subepithelial layer and forming ganglia cells during metamorphosis. Proliferation assays indicate a uniform distribution of dividing cells in the ectoderm across all developmental stages, suggesting the absence of distinct neurogenic zones with increased proliferation in gastropods.</p></sec><sec id="sec4001"><title>Discussion</title><p>Our findings reveal a spatially and temporally extended pattern of SoxB1 expression in a gastropod representative compared to other lophotrochozoan species. This prolonged and widespread expression of SoxB genes may be interpreted as a form of transcriptional neoteny, representing a preadaptation to prolonged neurogenesis. Consequently, it could contribute to the diversification of nervous systems in gastropods and lead to an increase in the complexity of the central nervous system in <italic>Mollusca</italic>.</p></sec>