Biology subjects

Justice, M. J.

Publications and source records attributed to Justice, M. J..

7 recordsLinked to original sources

bioRxiv2025

Visible traits demonstrate that crispant founder mice can be used for phenotypic assessment

Genes can be knocked out in model organisms by introducing a single guide RNA and Cas9 into one cell zygotes. Recently, the zebrafish and Xenopus communities have employed this method in genetic screening pipelines that assess phenotypes in founders (F0), referred to as "crispants". In contrast, phenotyping crispant mice has been avoided as results are believed to be confounded by genetic mosaicism, requiring that only established mouse lines undergo phenotypic assessment. Here, we targeted seven genes associated with visible recessive phenotypes. We observed the expected null phenotype in up to 100% founders per gene. Crucially, we achieved 100% editing efficiency in all but two animals. Genetic mosaicism was common, but did not confound an animals phenotype when comprised of mutations that all disrupted the targeted gene. Mosaicism included short in-frame mutations, but these were sufficient to disrupt function of five genes. Several founders were compound heterozygotes carrying a null and a non-null allele (short in-frame mutation or late truncation), enabling functional assessment of the non-null allele to dissect protein function. Our results set the stage for using crispant founders for initial phenotypic assessment in genetic screening, before selecting candidates for further study. This will dramatically reduce animal numbers.

genetics↗

bioRxiv2023

Trapping the exotic weevil Cnestus mutilatus with Isopropanol

The ambrosia beetle Cnestus mutilatus Blandford, 1894 (Coleoptera: Curculionidae: Scolytinae: Xyleborini) is native to Asia and is currently an exotic species in North America. This study tested whether this species can be trapped with isopropanol as bait. Lindgren multiple-funnel traps were deployed in the piedmont of south-central Virginia, USA. The experimental traps had isopropanol in the collection cups. For comparison, other traps had ethanol or soapy water. Both alcohols were effective for trapping C. mutilatus. More specimens were captured using ethanol. Isopropanol and ethanol may play similar roles in the chemical ecology of ambrosia beetles.

ecology↗

bioRxiv2023

A new mouse model of ATR-X syndrome carrying a common patient mutation exhibits neurological and morphological defects

ATRX is a chromatin remodelling ATPase that is involved in transcriptional regulation, DNA damage repair and heterochromatin maintenance. It has been widely studied for its role in ALT-positive cancers, but its role in neurological function remains elusive. Hypomorphic mutations in the X-linked ATRX gene cause a rare form of intellectual disability combined with alpha-thalassemia called ATR-X syndrome in hemizygous males. Patients also have facial dysmorphism, microcephaly, musculoskeletal defects and genital abnormalities. Since complete deletion of ATRX in mice results in early embryonic lethality, the field has largely relied on conditional knockout models to assess the role of ATRX in multiple tissues. Given that null alleles are not found in patients, a more patient-relevant model was needed. Here, we have produced and characterised the first patient mutation knock-in model of ATR-X syndrome, carrying the most common patient mutation, R246C. This is one of a cluster of missense mutations located in the chromatin interaction domain that disrupts its function. The knock-in mice recapitulate several aspects of the patient disorder, including craniofacial defects, microcephaly and impaired neurological function. They provide a powerful model for understanding the molecular mechanisms underlying ATR-X syndrome and for testing potential therapeutic strategies.

neuroscience↗

bioRxiv2021

Insect attraction to the six major types of traditional-style, residential light bulbs and implications for insect survival and light pollution

Artificial light at night can affect the behavior and survival of the arthropods attracted to it. Most light pollution research focuses on high-wattage street lamps, but lower-wattage lamps used to illuminate porches, paths, facades, and backyards vastly outnumber street lamps. Thus, residential consumers could potentially have an enormous influence on artificial light ecologies by their choice of lamp. This study compared insect attraction to the six major types of traditional-style, residential light bulb: incandescent, CFL, halogen, warm color temperature LED, cool color temperature LED, and the yellow "bug" lights marketed as reducing insect attraction. The bulbs were alternately used in a baffle-funnel light trap from early spring through late fall, and capture rates were determined for the orders of insects. Incandescent bulbs produced the highest trap captures; the warm color temperature LED bulb produced the fewest, even fewer than the yellow "bug" light. The yellow "bug" light attracted more Dermaptera (Leach) than the other bulbs. The data support a recommendation of LED bulbs, especially those with a warm color temperature, to minimize the effects of night lighting on insect behavior and mortality. Further, the use of yellow "bug" lights, in contrast to their marketing, could attract earwigs and other minor pests.

ecology↗

bioRxiv2021

A new murine Rpl5 (uL18) mutation provides a unique model of variably penetrant Diamond Blackfan Anemia

Ribosome dysfunction is implicated in multiple abnormal developmental and disease states in humans. Heterozygous germline mutations in genes encoding ribosomal proteins (RPs) are found in the majority of individuals with Diamond Blackfan anemia (DBA) while somatic mutations have been implicated in a variety of cancers and other disorders. Ribosomal protein-deficient animal models show variable phenotypes and penetrance, similar to human DBA patients. The spontaneous anemia remission observed in some DBA patients occurs via unknown mechanism(s) and has not been previously described in animal models. Here we characterized a novel ENU mouse mutant (Skax23m1Jus) with growth and skeletal defects, cardiac malformations and increased mortality. Following genetic mapping and whole exome sequencing, we identified an intronic Rpl5 mutation, which segregated with all affected mice. This mutation was associated with decreased ribosome generation, consistent with Rpl5 haploinsufficiency. Rpl5Skax23-Jus mutant animals had a profound delay in erythroid maturation and increased mortality at embryonic day E12.5, which improved by E14.5. Surviving mutant animals had a macrocytic anemia at birth as well as evidence of ventricular septal defect (VSD). Surviving adult and aged mice exhibited no hematopoietic defect or VSD. We propose that this novel Rpl5Skax23-Jus mutant mouse will be useful to study the factors influencing the variable penetrance and anemia remission that are observed in DBA.

developmental biology↗

bioRxiv2019

A resource of targeted mutant mouse lines for 5,061 genes

The International Mouse Phenotyping Consortium reports the generation of new mouse mutant strains for over 5,000 genes from targeted embryonic stem cells on the C57BL/6N genetic background. This includes 2,850 null alleles for which no equivalent mutant mouse line exists, 2,987 novel conditional-ready alleles, and 4,433 novel reporter alleles. This nearly triples the number of genes with reporter alleles and almost doubles the number of conditional alleles available to the scientific community. When combined with more than 30 years of community effort, the total mutant allele mouse resource covers more than half of the genome. The extensively validated collection is archived and distributed through public repositories, facilitating availability to the worldwide biomedical research community, and expanding our understanding of gene function and human disease.

genetics↗

bioRxiv2019

Suppressor mutations in Mecp2-null mice reveal that the DNA damage response is key to Rett syndrome pathology

Mutations in X-linked methyl-CpG-binding protein 2 (MECP2) cause Rett syndrome (RTT). We carried out a genetic screen for secondary mutations that improved phenotypes in Mecp2/Y mice after mutagenesis with N-ethyl-N-nitrosourea (ENU), aiming to identify potential therapeutic entry points. Here we report the isolation of 106 founder animals that show suppression of Mecp2-null traits from screening 3,177 Mecp2/Y genomes. Using exome sequencing, genetic crosses and association analysis, we identify 33 candidate genes in 30 of the suppressor lines. A network analysis shows that 61% of the candidate genes cluster into the functional categories of transcriptional repression, chromatin modification or DNA repair, delineating a pathway relationship with MECP2. Many mutations lie in genes that are predicted to modulate synaptic signaling or lipid homeostasis. Surprisingly, mutations in genes that function in the DNA damage response (DDR) also improve symptoms in Mecp2/Y mice. The combinatorial effects of multiple loci can be resolved by employing association analysis. One line, which was previously reported to carry a suppressor mutation in a gene required for cholesterol synthesis, Sqle, carries a second mutation in retinoblastoma binding protein 8 (Rbbp8 or CtIP), which regulates a DDR choice in double stranded break (DSB) repair. Cells from Mecp2/Y mice have increased DSBs, so this finding suggests that the balance between homology directed repair and non-homologous end joining is important for neuronal cells. In this and other lines, the presence of two suppressor mutations confers better symptom improvement than one locus alone, suggesting that combination therapies could be effective in RTT.

genetics↗