Current projects
Evolution and development of vertebrate lateral line system:
The development and evolution of electroreceptors in weakly electric fishes
- named PDRA on a
Leverhulme Trust research project grant to Professor Clare Baker, from 2025
Past projects
Evolution and development of vertebrate lateral line system:
Investigating the specification of hair cells versus electroreceptors in the lateral line using CRISPR/Cas9 in a sturgeon
- named PDRA on a BBSRC grant to Professor Clare Baker, ended 2019
- named PDRA on an Isaac Newton Trust grant to Professor Clare Baker, ended 2020
Abstract
In electroreceptive jawed fishes and amphibians, embryonic
lateral line placodes form lines of neuromasts on the head
and trunk, containing mechanosensory hair cells. Some or all
of the cranial neuromast lines are flanked by fields of
ampullary organs containing electroreceptors - modified hair
cells that respond to weak electric fields, such as those
surrounding other animals in water, including potential prey.
Previous reports of shared gene expression suggest that
conserved mechanisms underlie electroreceptor and mechanosensory
hair cell development and that electroreceptors evolved as a
transcriptionally related 'sister cell type' to hair cells.
We previously identified only one transcription factor gene,
Neurod4, as ampullary organ-restricted in the developing lateral
line system of a chondrostean ray-finned fish, the Mississippi
paddlefish (Polyodon spathula). We used our published lateral
line organ-enriched gene set (arising from differential bulk
RNA-seq in late-larval paddlefish), together with a candidate
gene approach, to identify 23 transcription factor genes
expressed in the developing lateral line system of a more
experimentally tractable chondrostean, the sterlet (Acipenser
ruthenus, a small sturgeon), and/or that of paddlefish.
Twelve are expressed in both ampullary organs and neuromasts,
consistent with conservation of molecular mechanisms. Six are
novel electrosensory-restricted transcription factor genes
(Irx5, Satb2, Insm1, Sp5, MafA and Rorc), and five are
the first-reported mechanosensory-restricted transcription factor
genes (Foxg1, Sox8, Isl1, Hmx2 and Rorb). Thus, we have
identified multiple transcription factors potentially involved
in the formation of electrosensory versus mechanosensory lateral
line organs. To test the function of selected candidates, we used
CRISPR/Cas9-mediated mutagenesis in F0-injected sterlet embryos.
We found that the 'hair cell' transcription factor gene Atoh1
is required for both hair cell and electroreceptor differentiation
in sterlet, and for Pou4f3 and Gfi1 expression in
both neuromasts and ampullary organs. These data support the
conservation of developmental mechanisms between hair cells and
electroreceptors. Targeting ampullary organ-restricted Neurod4
did not yield any phenotype, potentially owing to redundancy
with other Neurod genes that we found to be expressed
in sterlet ampullary organs. After targeting mechanosensory-restricted
Foxg1, ectopic ampullary organs formed within neuromast
lines, suggesting that Foxg1 normally represses their
development. We speculate that electrosensory organs may be
the 'default' fate of lateral line primordia in electroreceptive
vertebrates.
Comparative evo-devo studies of vertebrate attachment glands:
Ontogeny, evolution & homology of cement gland and attachment organs in lower vertebrates
- PhD project supervised by
Robert Cerny
- supported by the
STARS programme of the Faculty of Science, Charles University in Prague
- ended in 2017
Abstract
Cement glands or so called attachment organs are
larval cranial structures found in most
vertebrates with water-dwelling larval stages.
These structures secrete mucus that helps larvae
to attach to substrate or simply to stay at
their hatching place before their locomotory
organs are fully developed and before they can
feed. Morphology, topographic location on the
head, number of these glands/organs, but also
their embryonic origin significantly differ
among vertebrate lineages; their homology or
more exactly the level of their homology might
therefore be questioned. The key problem is
represented by mostly unknown fact that in basal
Actinopterygians like Polypterus (bichir) or
Amia (bowfin) (so called "ancient fishes") these
structures seem to be embryonically derived from
the pharyngeal endoderm whereas similar
structures of other vertebrates are of
superficial (ectodemal) origin. Moreover, in
Xenopus these structures are commonly considered
as a paradigm for anteriormost head patterning
with Otx2 gene expression. The goal of this
project is to identify developmental-genetic
mechanisms that drive morphogenesis of these
structures in several evolutionary key
vertebrate lineages. By using descriptive and
experimental methods of comparative embryology
we seek to study these structures in sturgeons,
bichirs and amphibians in order to identify
plesiomorphic and apomorphic features of
developmental-genetic modules of these organs
and thus to reveal key developmental changes
responsible for phenotypic variability of these
fundamental adaptive larval organs of
vertebrates.
Deciphering the evolution of cement organs in ray-finned fishes
- supported by
GAUK grant no. 220213
- ended in 2015
Abstract
Cement glands, one of the key vertebrate larval
adaptations, often are the first structures to
develop on the embryonic head. In vertebrates
they allow the larvae to attach to the
substrate. Although temporarily restricted, they
can have striking influence on craniofacial
development. Various types of cement glands have
been described in actinopterygians, dipnoans and
amphibians, similarly to ascidians and
lancelets. Although there are many studies on
their function and morphology, the question of
their homology remains unsolved. While cement
glands share many cytological characteristics of
secretory cells, they seem to differ
considerably in arrangement or embryonic origin.
Nevertheless, cement glands have recently been
defined as a result of shared capacity of larval
head ectoderm to express adhesive cells.
However, among actinopterygians these organs can
rise from different germ layers and in
dissimilar embryonic contexts. To assess their homology it is
therefore essential to understand their
evolution among actinopterygians first. This
project aims to provide a detailed
embryological, developmental and proteomic
characteristic of cement organs in key members
of Actinopterygii in order to understand their
developmental formation and evolution. This step
might help to elucidate evolution of these
adaptive structures of vertebrates in general.
Evolution of vertebrate foregut formation:
Contribution of pharyngeal morphogenesis into embryonic and larval adaptive structures of basal fishes: Micro-CT analyses of developmental processes and gene expression patterns
- supported by
Aktion Österreich-Tschechien scholarship
- autumn semester 2014/2015
Abstract (shortened)
Our previous data on bichir have demonstrated surprising endoderm
germ-layer origin of larval cement organs, a
transient mucus-secreting structures situated on
head surface of many vertebrate larvae which
enable a firm adhesion before mouth, fins or
limbs well develop. Whereas in other lineages
these organs derive paradigmatically from outer
ectoderm via epidermal thickening, in bichirs we
have revealed a strikingly dissimilar
morphogenesis via foregut-derived pouches, which
only later fuse with adjacent epidermis. Similar
developmental formation has also been suggested
for bowfins and gars, according to some
histology-based reports from the beginning of
20th century. Such situation contradicts the
general notion of pharyngeal endoderm as a
conservative germ layer with little or no
adaptive potential outside the foregut context.
This study aims to perform comparative analysis
of developmental formation and morphogenesis of
pharyngeal endoderm throughout embryogenesis to
identify its contribution to novel adaptive
traits. Concurrently, expression patterns of
candidate genes involved in these processes will
be evaluated in key fish lineages (bichirs,
sturgeons, bowfins, gars, teleosts).
MSc & BSc Projects:
Developmental morphogenesis of attachment organs in lower vertebrates
-
MSc Thesis supervised by Robert Cerny
-
BSc Thesis supervised by Robert Cerny
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