Biology subjects

Anderson, J. L.

Publications and source records attributed to Anderson, J. L..

7 recordsLinked to original sources

bioRxiv2024

WheresWalker: a pipeline for rapid mutation mapping using whole genome sequencing

Forward genetic screening is a powerful approach to assign functions to genes and can be used to elucidate the many genes whose functions remain unknown. Chemical mutagenesis is an unbiased and efficient method for generating point mutations in the founding generation of animals in a forward genetic screening experiment. Missense and nonsense mutations induced by chemical mutagenesis can lead to the generation of partial function, gain-of-function, or null alleles that underlie compelling phenotypes, but positional cloning of the underlying causative single base pair changes can be laborious and time-consuming, especially in large polymorphic genomes. Current methods use a bioinformatic mapping-by-sequencing approach which often identifies large genomic regions which contain an intractable number of candidate genes for testing. Here, we describe WheresWalker, a modern mapping-by-sequencing algorithm that identifies a mutation-containing interval and then supports positional cloning to refine the interval which drastically reduces the number of potential candidates allowing for extremely rapid mutation identification. We validated this method using mutants from a forward genetic mutagenesis screen in zebrafish for modifiers of ApoB-lipoprotein metabolism. WheresWalker correctly maps and identifies novel zebrafish mutations in mttp, apobb.1, and mia2 genes, as well as a previously published mutation in maize. Further, we use WheresWalker to identify a previously unappreciated ApoB-lipoprotein metabolism-modifying locus, slc3a2a.

genetics↗

bioRxiv2023

DNA binding analysis of rare variants in homeodomains reveals novel homeodomain specificity-determining residues

Homeodomains (HDs) are the second largest class of DNA binding domains (DBDs) among eukaryotic sequence-specific transcription factors (TFs) and play important roles in regulating development, body patterning, and cellular differentiation. Here, we analyzed 92 human HD mutants, including disease-associated variants and variants of unknown significance (VUSs), for their effects on DNA binding activity. Many of the variants altered DNA binding affinity and/or specificity. Biochemical analysis and structural modeling identified 14 novel specificity-determining positions, 5 of which do not contact DNA. The same missense substitution at analogous positions within different HDs often exhibited different effects on DNA binding. Variant effect prediction tools perform moderately well in distinguishing variants with altered binding affinity, but poorly in identifying those with altered specificity. Our results highlight the need for biochemical assays of TF coding variants and prioritize dozens of variants for further investigations into their pathogenicity and development of clinical diagnostics and precision therapies.

genetics↗

bioRxiv2022

Broad Recognition of Mamu-Bw4 and -A-related MHC class I Ligands by Rhesus Macaque Killer-Cell Immunoglobulin-Like Receptors

Definition of MHC class I ligands of rhesus macaque KIRs is fundamental to NK cell biology in this species as an animal model for infectious diseases, reproductive biology, and transplantation. To provide a more complete foundation for studying NK cell responses, rhesus macaque KIRs representing common allotypes of lineage II KIR genes were tested for interactions with MHC class I molecules representing diverse Mamu-A, -B, -E, -F, -I and -AG alleles. KIR-MHC class I interactions were identified by co-incubating reporter cell lines bearing chimeric KIR-CD3{zeta} receptors with target cells expressing individual MHC class I molecules and were corroborated by staining with KIR IgG-Fc fusion proteins. Ligands for 11 KIRs of previously unknown specificity were identified that fell into two general categories: interactions with multiple Mamu-Bw4 molecules or with Mamu-A-related molecules, including several allotypes of Mamu-AG and the hybrid Mamu-B*045:03 molecule. Although both groups include inhibitory and activating receptors, the majority of KIRs found to interact with Mamu-Bw4 are inhibitory, whereas most of the KIRs that interact with Mamu-AG are activating. We also identified Mamu-A1*012:01 as a ligand for KIR3DLw03*002, which belongs to a phylogenetically distinct group of macaque KIRs with a three amino acid deletion in D0 that is also present in human KIR3DL1/S1 and KIR3DL2. This study more than doubles the number of rhesus macaque KIRs with defined MHC class I ligands and identifies novel interactions with Mamu-AG, -B*045, and -A1*012. These findings support overlapping, but nonredundant, patterns of ligand recognition that reflects extensive functional diversification of these receptors.

immunology↗

bioRxiv2020

The developmental and genetic architecture of the sexually selected male ornament of swordtails

Sexual selection results in sex-specific characters like the conspicuously pigmented extension of the ventral tip of the caudal fin - the "sword" - in males of several species of Xiphophorus fishes. To uncover the genetic architecture underlying sword formation and to identify genes that are associated with its development, we characterized the sword transcriptional profile and combined it with genetic mapping approaches. Results showed that the male ornament of swordtails develops from a sexually non-dimorphic prepattern of transcription factors in the caudal fin. Among genes that constitute the exclusive sword transcriptome only two are located in the genomic region associated with this trait; the chaperone, fkbp9, and the potassium channel, kcnh8 that in addition to its neural function performs a role known to affect fin growth. This indicates that during evolution of swordtails a brain gene has been recruited for an additional function in establishing a male ornament.

evolutionary biology↗

bioRxiv2020

A Genetic Model Therapy Proposes a Critical Role for Liver Dysfunction in Mitochondrial Biology and Disease

The clinical and largely unpredictable heterogeneity of phenotypes in patients with mitochondrial disorders demonstrates the ongoing challenges in the understanding of this semi-autonomous organelle in biology and disease. Here we present a new animal model that recapitulates key components of Leigh Syndrome, French Canadian Type (LSFC), a mitochondrial disorder that includes diagnostic liver dysfunction. LSFC is caused by allelic variations in the Leucine Rich Pentatricopeptide repeat-containing motif (LRPPRC) gene. LRPPRC has native functions related to mitochondrial mRNA polyadenylation and translation as well as a role in gluconeogenesis. We used the Gene-Breaking Transposon (GBT) cassette to create a revertible, insertional mutant zebrafish line in the LRPPRC gene. lrpprc zebrafish homozygous mutants displayed impaired muscle development, liver function and lowered levels of mtDNA transcripts and are lethal by 12dpf, all outcomes similar to clinical phenotypes observed in patients. Investigations using an in vivo lipidomics approach demonstrated accumulation of non-polar lipids in these animals. Transcript profiling of the mutants revealed dysregulation of clinically important nuclearly encoded and mitochondrial transcripts. Using engineered liver-specific rescue as a genetic model therapy, we demonstrate survival past the initial larval lethality, as well as restored normal gut development, mitochondrial morphology and triglyceride levels functionally demonstrating a critical role for the liver in the pathophysiology of this model of mitochondrial disease. Understanding the molecular mechanism of the liver-mediated genetic rescue underscores the potential to improve the clinical diagnostic and therapeutic developments for patients suffering from these devastating disorders.

genetics↗

bioRxiv2020

Broad geographical and ecological diversity from similar genomic toolkits in the ascomycete genus Tetracladium

The ascomycete genus Tetracladium is best known for containing aquatic hyphomycetes, which are important decomposers in stream food webs. However, some species of Tetracladium are thought to be multifunctional and are also endobionts in plants. Suprisingly, Tetracladium sequences are increasingly being reported from metagenomics and metabarcoding studies of both plants and soils world-wide. It is not clear how these sequences are related to the described species and little is known about the non-aquatic biology of these fungi. Here, the genomes of 24 Tetracladium strains, including all described species, were sequenced and used to resolve relationships among taxa and to improve our understanding of ecological and genomic diversity in this group. All genome-sequenced Tetracladium fungi form a monophyletic group. Conspecific strains of T. furcatum from both aquatic saprotrophic and endobiont lifestyles and a putative cold-adapted clade are identified. Analysis of ITS sequences from water, soil, and plants from around the world reveals that multifunctionality may be widespread through the genus. Further, frequent reports of these fungi from extreme environments suggest they may have important but unknown roles in those ecosystems. Patterns of predicted carbohydrate active enzymes (CAZyme) and secondary metabolites in the Tetracladium genomes are more similar to each other than to other ascomycetes, regardless of ecology, suggesting a strong role for phylogeny shaping genome content in the genus. Tetracladium genomes are enriched for pectate lyase domains (including PL3-2), GH71 -1,3-glucanase domains and CBM24 -1,3-glucan/mutan binding modules, and both GH32 and CBM38, inulinase and inulin binding modules. These results indicate that these fungi are well-suited to digesting pectate and pectin in leaves when living as aquatic hyphomycetes, and inulin when living as root endobionts. Enrichment for -1,3-glucanase domains may be associated with interactions with biofilm forming microorganisms in root and submerged leaf environments.

evolutionary biology↗

bioRxiv2017

mRNA processing in mutant zebrafish lines generated by chemical and CRISPR-mediated mutagenesis produces potentially functional transcripts

As model organism-based research shifts from forward to reverse genetics approaches, largely due to the ease of genome editing technology, allow frequency of abnormal phenotypes is being observed in lines with mutations predicted to lead to deleterious effects on the encoded protein. In zebrafish, this low frequency is in part explained by compensation by genes of redundant or similar function, often resulting from the additional round of teleost-specific whole genome duplication within vertebrates. Here we offer additional explanations for the low frequency of mutant phenotypes. We analyzed mRNA processing in seven zebrafish lines with mutations expected to disrupt gene function, generated by CRISPR/Cas9 or ENU mutagenesis methods. Five of the seven lines showed evidence of genomic compensation by means of altered mRNA processing: one through a skipped exon that did not lead to a frame shift, one through nonsense-associated splicing that did not lead to a frame shift, and three through the use of cryptic splice sites. These results highlight the need for a methodical analysis of the mRNA produced in mutant lines before making conclusions or embarking on studies that assume loss of function as a result of a given genomic change. Furthermore, recognition of the types of genomic adaptations that can occur may inform the strategies of mutant generation.\n\nAuthor summaryThe recent rise of reverse genetic, gene targeting methods has allowed researchers to readily generate mutations in any gene of interest with relative ease. Should these mutations have the predicted effect on the mRNA and encoded protein, we would expect many more abnormal phenotypes than are typically being seen in reverse genetic screens. Here we set out to explore some of the reasons for this discrepancy by studying seven separate mutations in zebrafish. We present evidence that thorough cDNA sequence analysis is a key step in assessing the likelihood that a given mutation will produce hypomorphic or null alleles. This study reveals that alternative mRNA processing in the mutant background often produces transcripts that escape nonsense-mediated decay, thereby potentially preserving gene function. By understanding the ways that cells avoid the deleterious consequences of mutations, researchers can better design reverse genetic strategies to increase the likelihood of gene disruption.

molecular biology↗