Hempel, M. | bioRxiv Science

bioRxiv2021

Marker-assisted mapping enables effective forward genetic analysis in the arboviral vector Aedes aegypti, a species with vast recombination deserts

Aedes aegypti is a major vector of arboviruses that cause dengue, chikungunya, yellow fever and Zika. Although recent success in reverse genetics has facilitated rapid progress in basic and applied research, integration of forward genetics with modern technologies remains challenging in this important species, as up-to-47% of its chromosome is refractory to genetic mapping due to extremely low rate of recombination. Here we report the development of a marker-assisted-mapping (MAM) strategy to readily screen for and genotype only the rare but informative recombinants, drastically increasing both the resolution and signal-to-noise ratio. Using MAM, we mapped a transgene that was inserted in a >100 Mb recombination desert and a sex-linked spontaneous red-eye (re) mutation just outside the region. We subsequently determined, by CRISPR/Cas9-mediated knockout, that cardinal is the causal gene of re, which is the first forward genetic identification of a causal gene in Ae. aegypti. This study provides the molecular foundation for using gene-editing to develop versatile and stable genetic sexing methods by improving upon the current re-based genetic sexing strains. MAM does not require densely populated markers and can be readily applied throughout the genome to facilitate the mapping of genes responsible for insecticide- and viral-resistance. By enabling effective forward genetic analysis, MAM bridges a significant gap in establishing Ae. aegypti as a model system for research in vector biology. As large regions of suppressed recombination are also common in other plant and animal species including those of economic significance, MAM will have broad applications beyond vector biology.

genetics↗

bioRxiv2017

Survival Beyond the Perinatal Period Expands the Phenotypes Caused by Mutations in GLE1

Mutations in GLE1 underlie Lethal Congenital Contracture syndrome (LCCS1) and Lethal Arthrogryposis with Anterior Horn Cell Disease (LAAHD). Both LCCS1 and LAAHD are characterized by reduced fetal movements, congenital contractures, and a severe form of motor neuron disease that results in fetal death or death in the perinatal period, respectively. Via trio-exome sequencing, we identified bi-allelic mutations in GLE1 in two unrelated individuals with motor delays, feeding difficulties and respiratory insufficiency who survived beyond the perinatal period. Each affected child had missense variants predicted to result in amino acid substitutions near the C-terminus of GLE1 that are predicted to disrupt protein-protein interaction or GLE1 protein targeting. We hypothesize that mutations that preserve function of the coiled-coil domain of GLE1 cause LAAHD whereas mutations that abolish the function of the coiled-coil domain cause LCCS1. The phenotype of LAAHD is now expanded to include multiple individuals surviving into childhood suggesting that LAAHD is a misnomer and should be re-named Arthrogryposis with Anterior Horn Cell Disease (AAHD). Too few cases have been reported to identify significant genotype-phenotype relationships, but given that perinatal lethality in AAHD typically resulted from respiratory failure, it is possible that early or aggressive airway management such as early tracheostomy and ventilation may enable survival beyond the perinatal period.

genetics↗