Biology subjects

Flannery, K. P.

Publications and source records attributed to Flannery, K. P..

3 recordsLinked to original sources

bioRxiv2026

Removal of maternal compensation reveals retinal-specific roles for Pomgnt1 in zebrafish

Genetic variants in Protein O-mannose N-acetylglucosaminyltransferase 1 (POMGNT1) result in a broad spectrum of disorders, ranging from severe congenital muscular dystrophy with brain and ocular malformations to non-syndromic retinitis pigmentosa. Despite POMGNT1's established role in the glycosylation of the transmembrane glycoprotein &alpha-dystroglycan (&alpha-DG), the mechanistic basis for this clinical variability remains poorly understood. Previous work in a zebrafish pomngt1 knock-out (KO) line identified retinal degeneration at 6 months post-fertilization (mpf). However, potential involvement of other tissues was not characterized, and compensation from maternal transcripts which can occur in the zebrafish oocyte was not tested. Here, we analyzed maternal-zygotic pomgnt1 KOs (MZKOs) to determine whether maternal compensation influences the onset and severity of pomgnt1-associated phenotypes. We assessed survival, gross morphology, locomotor activity, behavioral patterns, and retinal organization across multiple timepoints. MZKOs survived to adulthood and exhibited no morphological or locomotor deficits up to 5 mpf. Retinal abnormalities were found as early as 2 mpf in MZKOs, demonstrating that maternally provided factors of pomgnt1 delay the onset of retinal pathology. Additionally, MZKOs displayed a novel wall-hugging behavioral pattern that may be consistent with visual impairment or anxiety. These findings demonstrate a strong tissue-specific phenotype following loss of pomgnt1 in zebrafish showing evolutionary divergence in the necessity for Pomgnt1 function in the muscle. However, this strain provides a useful system for investigating the mechanisms underlying the retinal vulnerability observed in POMGNT1-related retinitis pigmentosa.

genetics↗

bioRxiv2025

Impact of maternal compensation on developmental phenotypes in a zebrafish model of severe congenital muscular dystrophy

Genetic compensation is a common phenomenon in zebrafish in response to genetic alterations. As such, differences between morphant and mutant zebrafish models of human diseases have led to significant difficulties in phenotypic interpretation and translatability. One form of compensation is the maternal deposit of mRNAs and proteins into the oocyte that supports developmental processes before zygotic genome activation. In this study, we generated a zebrafish model of severe congenital muscular dystrophy by targeting protein O-mannose N-Acetylglucosaminyltransferase 2 (pomgnt2), a maternally provided gene that maintains cell-extracellular matrix interactions through glycosylation. Zygotic knockouts (ZKOs) retain protein function in the first week post-fertilization and survive to adulthood, though they develop muscle disease later in life. In contrast, maternal-zygotic KOs (MZKOs) generated from ZKO females develop early-onset muscle disease, reduced motor function, neuronal axon guidance deficits, and retinal synapse disruptions, recapitulating features of the human presentation. While assessing transcriptional changes linked to disease progression, the availability of embryos obtained from different breeding strategies also allowed for direct comparison of ZKOs and MZKOs to define the impact of having a KO mother. We found that offspring from a ZKO mother, independently of genotype, show distinct expression patterns from animals obtained from heterozygous breeding. Some of these changes reflect an increased metabolic requirement, possibly stemming from maternal metabolic disruption. These findings will not only be applicable to other CMD models targeting maternally provided genes but also provide new insight into modeling disease using maternal-zygotic mutants.

genetics↗

bioRxiv2022

Removal of pomt1 in zebrafish leads to loss of α-dystroglycan glycosylation and dystroglycanopathy phenotypes

Biallelic mutations in Protein O-mannosyltransferase 1 (POMT1) are among the most common causes of a severe group of congenital muscular dystrophies (CMDs) known as dystroglycanopathies. POMT1 is a glycosyltransferase responsible for the attachment of a functional glycan mediating interactions between the transmembrane glycoprotein dystroglycan and its binding partners in the extracellular matrix (ECM). Disruptions in these cell-ECM interactions lead to multiple developmental defects causing brain and eye malformations in addition to CMD. Removing Pomt1 in the mouse leads to early embryonic death due to the essential role of dystroglycan during placental formation in rodents. Here, we characterized and validated a model of pomt1 loss of function in the zebrafish showing that developmental defects found in individuals affected by dystroglycanopathies can be recapitulated in the fish. We also discovered that pomt1 mRNA provided by the mother in the oocyte supports dystroglycan glycosylation during the first few weeks of development. Muscle disease, retinal synapse formation deficits, and axon guidance defects can only be uncovered during the first week post fertilization by generating knock-out embryos from knock-out mothers. Conversely, maternal pomt1 from heterozygous mothers was sufficient to sustain muscle, eye, and brain development only leading to loss of photoreceptor synapses at 30 days post fertilization. Our findings show that it is important to define the contribution of maternal mRNA while developing zebrafish models of dystroglycanopathies and that offspring generated from heterozygous and knock-out mothers can be used to differentiate the role of dystroglycan glycosylation in tissue formation and maintenance.

neuroscience↗