The liver is a central organ with essential roles in processes such as nutritional metabolism, detoxification, and immune defense[1][1]–[6][2]. It has been instrumental in the adaptation of mammalian species to diverse environments, as reflected by its rapid molecular evolution[7][3],[8][4]. However, the origins and evolutionary dynamics of liver cell types and their structural organization remain largely unexplored. Here we report evolutionary analyses of transcriptome and chromatin accessibility data for liver cells from 17 species, spanning all major feeding strategies (herbivory, omnivory, carnivory, insectivory), great apes (including humans), placental clades (Afrotheria, Xenarthra, Laurasiatheria, Euarchontoglires), major mammalian lineages (placentals, marsupials, monotremes), and a bird as outgroup. Integrated with spatial transcriptomics, our data reveal that liver zonation—the compartmentalization of hepatocyte functions along the lobule, the liver’s fundamental anatomical and functional unit—is conserved across mammals but absent in other vertebrates. We find that zonation originated in the mammalian ancestor, driven by the emergence of WNT and R-spondin signaling from central vein endothelial cells, which activate central hepatocyte gene expression via the transcription factor TCF7L2. Despite this conserved architecture and signaling, genes with zonated expression exhibit rapid evolutionary turnover. Consistently, hepatocytes evolve fast, likely due to reduced selective constraints, enabling adaptive changes under positive selection. Alongside immune cells, hepatocytes are therefore key drivers of the liver’s rapid evolution and functional innovations. In great apes, we identify human-specific shifts in zonation and cell-type-specific expression linked to recent cis-regulatory changes, particularly in genes involved in lipid metabolism, likely contributing to human-specific metabolic traits. Our study uncovers the origins of a mammal-specific liver cell architecture, within which reduced constraints facilitated molecular changes underlying ecological adaptations. ### Competing Interest Statement The authors have declared no competing interest. [1]: #ref-1 [2]: #ref-6 [3]: #ref-7 [4]: #ref-8

The Sex-linked orange mutation in domestic cats causes variegated patches of reddish/yellow hair and is a defining signature of random X inactivation in female tortoiseshell and calico cats. Unlike the situation for most coat color genes, there is no apparent homolog for Sex-linked orange in other mammals. We show that Sex-linked orange is caused by a 5-kb deletion that leads to ectopic and melanocyte-specific expression of the Rho GTPase Activating Protein 36 (Arhgap36) gene. Single-cell RNA sequencing (RNA-seq) studies from fetal cat skin reveal that red/yellow hair color is caused by reduced expression of melanogenic genes that are normally activated by the melanocortin 1 receptor (Mc1r)-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway, but Mc1r and its ability to stimulate cAMP accumulation is intact. Instead, we show that expression of Arhgap36 in melanocytes leads to reduced levels of the PKA catalytic subunit (PKAC); thus, Sex-linked orange is genetically and biochemically downstream of Mc1r. Our findings resolve a longstanding comparative genetic puzzle, provide in vivo evidence for the ability of Arhgap36 to inhibit PKA, and reveal a molecular explanation for a charismatic color pattern with a rich genetic history.

There have been rapid advancements in genomic medicine, but because of systemic factors that lead to barriers in healthcare access, these benefits are not equally available to all individuals. Social Determinants of Health (SDoH) are elements outside of genetic or medical conditions such as income, geography, and education, and they have been shown to account for up to 47% of overall health outcomes in patients within the United States. We are employing the genomic, phenotypic, and survey data provided by the All of Us Research Program to identify biological and SDoH factors that influence the presentation and diagnosis of neurofibromatosis type 1 (NF1).

PURPOSE:We compared the rate of errors in genome sequencing (GS) result disclosures by genetic counselors (GC) and trained non-genetics healthcare professionals (NGHPs) in SouthSeq, a randomized trial utilizing GS in critically ill infants. METHODS:Over 400 recorded GS result disclosures were analyzed for major and minor errors. We used Fisher's exact test to compare error rates between GCs and NGHPs and performed a qualitative content analysis to characterize error themes. RESULTS:Major errors were identified in 7.5% of disclosures by NGHPs and in no disclosures by GCs. Minor errors were identified in 32.1% of disclosures by NGHPs and in 11.4% of disclosures by GCs. Although most disclosures lacked errors, NGHPs were significantly more likely to make any error than GCs for all result types (positive, negative, or uncertain). Common major error themes include omission of critical information, overstating a negative result, and overinterpreting an uncertain result. The most common minor error was failing to disclose negative secondary findings. CONCLUSION:Trained NGHPs made clinically significant errors in GS result disclosures. Characterizing common errors in result disclosure can illuminate gaps in education to inform the development of future genomics training and alternative service delivery models.

The Bengal cat breed was developed from intercrosses between the Asian leopard cat, Prionailurus bengalensis, and the domestic cat, Felis catus, with a last common ancestor approximately 6 million years ago. Predicted to derive ∼94% of their genome from domestic cats, regions of the leopard cat genome are thought to account for the unique pelage traits and ornate color patterns of the Bengal breed, which are similar to those of ocelots and jaguars. We explore ancestry distribution and selection signatures in the Bengal breed by using reduced representation and whole-genome sequencing from 947 cats. The mean proportion of leopard cat DNA in the Bengal breed is 3.48%, lower than predicted from breed history, and is broadly distributed, covering 93% of the Bengal genome. Overall, leopard cat introgressions do not show strong signatures of selection across the Bengal breed. However, two popular color traits in Bengal cats, charcoal and pheomelanin intensity, are explained by selection of leopard cat genes whose expression is reduced in a domestic cat background, consistent with genetic incompatibility resulting from hybridization. We characterize several selective sweeps in the Bengal genome that harbor candidate genes for pelage and color pattern and that are associated with domestic, rather than leopard, cat haplotypes. We identify the molecular and phenotypic basis of one selective sweep as reduced expression of the Fgfr2 gene, which underlies glitter, a trait desired by breeders that affects hair texture and light reflectivity.

Genomic studies of endangered species have primarily focused on describing diversity patterns and resolving phylogenetic relationships, with the overarching goal of informing conservation efforts. However, few studies have investigated genomic diversity housed in captive populations. For tigers ( Panthera tigris ), captive individuals vastly outnumber those in the wild, but their diversity remains largely unexplored. Privately owned captive tiger populations have remained an enigma in the conservation community, with some believing that these individuals are severely inbred, while others believe they may be a source of now-extinct diversity. Here, we present a large-scale genetic study of the private (non-zoo) captive tiger population in the United States, also known as “Generic” tigers. We find that the Generic tiger population has an admixture fingerprint comprising all six extant wild tiger subspecies. Of the 138 Generic individuals sequenced for the purpose of this study, no individual had ancestry from only one subspecies. We show that the Generic tiger population has a comparable amount of genetic diversity relative to most wild subspecies, few private variants, and fewer deleterious mutations. We observe inbreeding coefficients similar to wild populations, although there are some individuals within both the Generic and wild populations that are substantially inbred. Additionally, we develop a reference panel for tigers that can be used with imputation to accurately distinguish individuals and assign ancestry with ultralow coverage (0.25×) data. By providing a cost-effective alternative to whole-genome sequencing (WGS), the reference panel provides a resource to assist in tiger conservation efforts for both ex- and in situ populations.

The Alabama Genomic Health Initiative (AGHI) is a state-funded, IRB-approved study that since 2017 has pursued the goals of providing access to genomic technologies to a diverse population and exploring the utility and impact of population-based screening for rare Mendelian disorders. In 2021, the AGHI, a collaboration between the University of Alabama at Birmingham (UAB) and the HudsonAlpha Institute for Biotechnology, partnered with UAB Family and Community Medicine to recruit participants for population-based screening and return medically-actionable results to both participants and their primary care providers.

Background: It is critical to understand the wide-ranging clinical and non-clinical effects of genome sequencing (GS) for parents in the NICU context. We assessed parents’ experiences with GS as a first-line diagnostic tool for infants with suspected genetic conditions in the NICU. Methods: Parents of newborns (N = 62) suspected of having a genetic condition were recruited across five hospitals in the southeast United States as part of the SouthSeq study. Semi-structured interviews (N = 78) were conducted after parents received their child’s sequencing result (positive, negative, or variants of unknown significance). Thematic analysis was performed on all interviews. Results: Key themes included that (1) GS in infancy is important for reproductive decision making, preparing for the child’s future care, ending the diagnostic odyssey, and sharing results with care providers; (2) the timing of disclosure was acceptable for most parents, although many reported the NICU environment was overwhelming; and (3) parents deny that receiving GS results during infancy exacerbated parent–infant bonding, and reported variable impact on their feelings of guilt. Conclusion: Parents reported that GS during the neonatal period was useful because it provided a “backbone” for their child’s care. Parents did not consistently endorse negative impacts like interference with parent–infant bonding.

1 HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, United States of America, 2 Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America, 3 School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin, Ireland, 4 Department of Biology and the Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America, 5 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America, 6 Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany, 7 Environmental Genomics, Christian-Albrechts University of Kiel, Kiel, Germany, 8 Max Planck Institute for Evolutionary Biology, Plön, Germany

As the uptake of population screening expands, assessment of medical and psychosocial outcomes is needed. Through the Alabama Genomic Health Initiative (AGHI), a state-funded genomic research program, individuals received screening for pathogenic or likely pathogenic variants in 59 actionable genes via genotyping. Of the 3874 eligible participants that received screening results, 858 (22%) responded to an outcomes survey. The most commonly reported motivation for seeking testing through AGHI was contribution to genetic research (64%). Participants with positive results reported a higher median number of planned actions (median = 5) due to AGHI results as compared to negative results (median = 3). Interviews were conducted with survey participants with positive screening results. As determined by certified genetic counselors, 50% of interviewees took appropriate medical action based on their result. There were no negative or harmful actions taken. These findings indicate population genomic screening of an unselected adult population is feasible, is not harmful, and may have positive outcomes on participants now and in the future; however, further research is needed in order to assess clinical utility.

OBJECTIVES/GOALS: Supported by the State of Alabama, the Alabama Genomic Health Initiative (AGHI) is aimed at preventing and treating common conditions with a genetic basis. This joint UAB Medicine-HudsonAlpha Institute for Biotechnology effort provides genomic testing, interpretation, and counseling free of charge to residents in each of Alabama’s 67 counties. METHODS/STUDY POPULATION: Launched in 2017, as a state-wide population cohort, AGHI (1.0) enrolled 6,331 Alabamians and returned individual risk of disease(s) related to the ACMG SF v2.0 medically actionable genes. In 2021, the cohort was expanded to include a primary care cohort. AGHI (2.0) has enrolled 750 primary care patients, returning individual risk of disease(s) related to the ACMG SF v3.1 gene list and pre-emptive pharmacogenetics (PGx) to guide medication therapy. Genotyping is done on the Illumina Global Diversity Array with Sanger sequencing to confirm likely pathogenic / pathogenic variants in medically actionable genes and CYP2D6 copy number variants using Taqman assays, resulting in a CLIA-grade report. Disease risk results are returned by genetic counselors and Pharmacogenetics results are returned by Pharmacists. RESULTS/ANTICIPATED RESULTS: We have engaged a statewide community (>7000 participants), returning 94 disease risk genetic reports and 500 PGx reports. Disease risk reports include increased predisposition to cancers (n=38), cardiac diseases (n=33), metabolic (n=12), other (n=11). 100% of participants harbor an actionable PGx variant, 70% are on medication with PGx guidance, 48% harbor PGx variants and are taking medications affected. In 10% of participants, pharmacists sent an active alert to the provider to consider/ recommend alternative medication. Most commonly impacted medications included antidepressants, NSAIDS, proton-pump inhibitors and tramadol. To enable the EMR integration of genomic information, we have developed an automated transfer of reports into the EMR with Genetics Reports and PGx reports viewable in Cerner. DISCUSSION/SIGNIFICANCE: We share our experience on pre-emptive implementation of genetic risk and pharmacogenetic actionability at a population and clinic level. Both patients and providers are actively engaged, providing feedback to refine the return of results. Real time alerts with guidance at the time of prescription are needed to ensure future actionability and value.

SUMMARYColor variation is a frequent evolutionary substrate for camouflage in small mammals but the underlying genetics and evolutionary forces that drive color variation in natural populations of large mammals are mostly unexplained. The American black bear, Ursus americanus, exhibits a range of colors including the cinnamon morph which has a similar color to the brown bear, U. arctos, and is found at high frequency in the American southwest. Reflectance and chemical melanin measurements showed little distinction between U. arctos and cinnamon U. americanus individuals. We used a genome-wide association for hair color as a quantitative trait in 151 U. americanus individuals and identified a single major locus (P < 10−13). Additional genomic and functional studies identified a missense alteration (R153C) in Tyrosinase-related protein 1 (TYRP1) that impaired protein localization and decreased pigment production. Population genetic analyses and demographic modeling indicated that the R153C variant arose 9.36kya in a southwestern population where it likely provided a selective advantage, spreading both northwards and eastwards by gene flow. A different TYRP1 allele, R114C, contributes to the characteristic brown color of U. arctos, but is not fixed across the range.HIGHLIGHTSThe cinnamon morph of American black bears and brown bears have different missense mutations in TYRP1 that account for their similar colorationTYRP1 variants in American black bears and brown bears are loss-of-function alleles associated with impaired protein localization to melanosomesIn American black bears, the variant causing the cinnamon morph arose 9,360 years ago in the western lineage where it provides an adaptive advantage, and has spread northwards and eastwards by migration

As traditional barriers to the use of genome sequencing decrease, it is likely that the application of this testing will exceed the available capacity of geneticists and genetic counselors to disclose results. Various methods for extending the capacity of genetics providers have been explored, including training of non-genetics providers in genomic results disclosures. In SouthSeq, part of the Clinical Sequencing Evidence-Generating Research Consortium, genome sequencing is used as a first-line diagnostic tool for critically-ill infants with suspected genetic disorders; results are returned by either genetic counselors or trained non-genetics providers.

To meet current and expected future demand for genome sequencing in the neonatal intensive care unit (NICU), adjustments to traditional service delivery models are necessary. Effective programs for the training of non-genetics providers (NGPs) may address the known barriers to providing genetic services including limited genetics knowledge and lack of confidence. The SouthSeq project aims to use genome sequencing to make genomic diagnoses in the neonatal period and evaluate a scalable approach to delivering genome sequencing results to populations with limited access to genetics professionals. Thirty-three SouthSeq NGPs participated in a live, interactive training intervention and completed surveys before and after participation. Here, we describe the protocol for the provider training intervention utilized in the SouthSeq study and the associated impact on NGP knowledge and confidence in reviewing, interpreting, and using genome sequencing results. Participation in the live training intervention led to an increased level of confidence in critical skills needed for real-world implementation of genome sequencing. Providers reported a significant increase in confidence level in their ability to review, understand, and use genome sequencing result reports to guide patient care. Reported barriers to implementation of genome sequencing in a NICU setting included test cost, lack of insurance coverage, and turn around time. As implementation of genome sequencing in this setting progresses, effective education of NGPs is critical to provide access to high-quality and timely genomic medicine care.

The Alabama Genomic Health Initiative (AGHI) is a state-supported, IRB-approved research study, that began in 2017 to explore the utility and impact of population-based screening for rare Mendelian disorders, and has helped to serve as a model and platform for other participant-facing programs. Over the last year a new model has been developed that is focused on health care providers, with a primary goal to bring and apply genomic knowledge in a primary care setting.

Genome sequencing (GS) may shorten the diagnostic odyssey and guide clinical management in infants with suspected genetic disorders. GS detects a variety of genetic variant types (SNVs, indels, CNVs, aneuploidy) and permits phenotype-independent variant assessment, which is important in infants whose clinical presentation may not be well-defined until later in life. In SouthSeq, part of the Clinical Sequencing Evidence-Generating Research Consortium, we evaluated GS as a first-line diagnostic tool for infants with suspected but undiagnosed genetic disorders.