Biology subjects

Zitova, A.

Publications and source records attributed to Zitova, A..

3 recordsLinked to original sources

bioRxiv2026

Pax6-dependent patterning in an annelid informs the evolution of bilaterian nerve cords

Conserved dorsoventral patterning systems have been proposed as evidence for a common evolutionary origin of centralized nervous systems in Bilateria, yet functional evidence outside vertebrates and arthropods remains limited. Here, we investigated the role of pax6 in the annelid Platynereis dumerilii using a mutant carrying a 61 bp deletion in the paired-domain coding region. Loss of pax6 disrupted ventral neuroectodermal patterning at 34 hpf, causing a shift in nk2.2 expression, narrowing of the nk6 domain, and downregulation of pax3/7, while msx expression remained largely unaffected. These early patterning defects were followed by selective neuronal abnormalities at 48 hpf, including displacement of TrpH-positive serotonergic cells and loss of posterior hb9-positive motoneuron domains. By 6 dpf, additional defects were observed in TrpH, ChAT, VAChT, and nk2.2 expression, accompanied by severe disruption of ventral nerve cord morphology and loss of the characteristic rope-ladder architecture. Together, these findings identify pax6 as a key regulator linking dorsoventral progenitor patterning, neuronal subtype specification, and nervous system morphogenesis in Platynereis. Our results provide functional evidence that the conserved dorsoventral patterning network plays an essential role in annelid ventral nerve cord development and support the view that important components of bilaterian nervous system patterning predate the divergence of major animal lineages.

evolutionary biology↗

bioRxiv2025

Pax6 maintains lens epithelial cell identity and coordinates secondary fiber cell differentiation

Pax6 is a crucial regulator of vertebrate eye development, and its loss leads to the failure of lens placode formation. To investigate Pax6 function at successive stages of lens development, we employed the Cre-loxP system in combination with a novel Foxe3-Cre driver, which becomes active after the lens placode stage but prior to the onset of secondary fiber cell differentiation. The Foxe3-Cre enables efficient deletion of Pax6 throughout the entire lens by embryonic day E12.5. Our study shows that Pax6 loss causes a delay in lens differentiation, disrupts the lens epithelium, and produces a smaller lens that remains attached to the cornea, ultimately leading to a rudimentary lens in adulthood. Notably, Foxe3 persisted in the mutant lens epithelium despite Pax6 loss, while apoptosis and aberrant Sox2 upregulation occurred in the epithelium. Combined with the delayed onset of fiber cell differentiation, the abnormal anterior expansion of fiber cell differentiation regulators (c-Maf and Sox1), and the aberrant expression of cyclin D2, these results underscore the essential role of Pax6 in preserving lens epithelial identity and coordinating the transition to secondary fiber cell differentiation.

developmental biology↗

bioRxiv2024

Cell type and regulatory analysis in amphioxus illuminates evolutionary origin of the vertebrate head

To shed light on the enigmatic origin of the vertebrate head, our study employs an integrated approach that combines single-cell transcriptomics, perturbations in signalling pathways, and cis-regulatory analysis in amphioxus, a close relative of chordate common ancestor. Through cell type characterization, we identified the presence of a prechordal plate, pre-migratory and migratory neural crest-like cell populations in the developing amphioxus embryo. Functional analysis established conserved roles of the Nodal and Hedgehog signalling pathways in prechordal plate, and of Wnt signalling pathway in neural crest development. Furthermore, the trans-species transgenic experiments provided evidence of cis-regulatory level homology within the chordate lineage. Our findings provide evidence that the key features of vertebrate head development can be traced back to the common ancestor of all chordates. One Sentence SummaryCell populations forming the vertebrate head are present in the close relative of chordate common ancestor.

evolutionary biology↗