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Holoprosencephaly and cyclopia in bmp7b and bmpr1ba Crispant zebrafish
Valentyn Kyrychenko1, Philipp Rensinghoff1, Johannes Bulk1
1Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Insights
Holoprosencephaly (HPE) is a forebrain developmental disorder where the anterior neural plate fails to divide. Zebrafish models targeting bmp7b and bmpr1ba show HPE, offering a new research approach.
Area of Science:
- Developmental Biology
- Neuroscience
- Genetics
Background:
- Holoprosencephaly (HPE) is the most common forebrain developmental disorder, characterized by the failure of the anterior neural plate (ANP) to properly divide.
- Bone morphogenetic protein (BMP) signaling is crucial for nervous system development, with both signaling and antagonism playing significant roles.
Purpose of the Study:
- To investigate the roles of the BMP ligand bmp7b and the receptor bmpr1ba in zebrafish forebrain development.
- To establish a novel zebrafish model for studying HPE using CRISPR/Cas9 technology.
Main Methods:
- Transient CRISPR/Cas9 targeting of bmp7b and bmpr1ba in zebrafish.
- Analysis of forebrain and eye field morphology and gene expression patterns in crisplant zebrafish.
- Comparison with known HPE induction by bmp4.
Main Results:
- Zebrafish crisplants for both bmp7b and bmpr1ba exhibited HPE and cyclopia (a single central eye).
- In bmp7b crisplants, the anterior neural plate (ANP) was affected, with key eye field markers (rx3, six3b, cxcr4a) showing midline condensation.
- Induced expression of bmp4, a known cause of HPE, altered bmpr1ba expression.
Conclusions:
- Zebrafish crisplants for bmp7b and bmpr1ba represent a viable novel model for studying HPE.
- CRISPR/Cas9 targeting offers advantages for HPE research, enabling analyses without the need for traditional mutant lines.
- Further research should explore the specific roles of individual BMP ligands, receptors, and antagonists in forebrain development and HPE pathogenesis.
Abstract:
Holoprosencephaly (HPE) is the most frequent developmental disorder of the forebrain. In HPE, the early single anlage of the forebrain, the anterior neural plate (ANP) which encompasses the future telencephalon and eye field, fails to divide. BMP signaling and antagonism are overall important for nervous system development. The focus of this study was on the role of the ligand bmp7b and the receptor bmpr1ba during forebrain development. The zebrafish loci of bmp7b and bmpr1ba were targeted transiently with CRISPR/Ca9. Crispants for both bmp7b and bmpr1ba presented HPE and cyclopia, one central eye. Subsequently, the ANP was addressed in bmp7b Crispants. The morphology of the eye field was affected, with important markers, rx3, six3b and cxcr4a expressed condensed at the midline. Induced expression of bmp4 is also known to result in HPE. Such bmp4 induction altered the expression of bmpr1ba. Zebrafish Crispants for bmp7b and bmpr1ba can be used as a novel HPE model. A challenge in future analyses will be the penetrance of phenotypes in Crispants. The advantages are, however, that analyses can be conducted anywhere, without the need of mutant lines. One important aspect for future analysis will be the role of individual bmp ligands, receptors and antagonists in forebrain development.
