Of mice and men - and guinea pigs?

Single-cell analysis of preimplantation embryonic development in guinea pigs

BACKGROUND

Guinea pigs exhibit numerous physiological similarities to humans, yet the details of their preimplantation embryonic development remain largely unexplored.

RESULTS

To address this, we conducted single-cell sequencing on the transcriptomes of cells isolated from the zygote stage through preimplantation stages in guinea pigs. This study identified seven distinct cell types within guinea pig preimplantation embryos and pinpointed the timing of zygotic gene activation (ZGA). Trajectory analysis revealed a bifurcation into two lineage-specific branches, accompanied by alterations in specific pathways, including oxidative phosphorylation and vascular endothelial growth factor (VEGF). Additionally, co-expressed gene network analysis highlighted the most enriched functional modules for the epiblast (EPI), primitive endoderm (PrE), and inner cell mass (ICM). Finally, we compared the similarities and differences between human and guinea pig epiblasts (EPIs).

CONCLUSION

This study systematically constructs a cell atlas of guinea pig preimplantation embryonic development, offering fresh insights into mammalian embryonic development and providing alternative experimental models for studying human embryonic development.

Pitfalls of using sequence databases for heterologous expression studies - a technical review

Synthesis of DNA fragments based on gene sequences that are available in public resources has become an efficient and affordable method that has gradually replaced traditional cloning efforts such as PCR cloning from cDNA. However, database entries based on genome sequencing results are prone to errors which can lead to false sequence information and, ultimately, errors in functional characterisation of proteins such as ion channels and transporters in heterologous expression systems. We have identified five common problems that repeatedly appear in public resources: (1) Not every gene has yet been annotated; (2) not all gene annotations are necessarily correct; (3) transcripts may contain automated corrections; (4) there are mismatches between gene, mRNA and protein sequences; and (5) splicing patterns often lack experimental validation. This technical review highlights and provides a strategy to bypass these issues in order to avoid critical mistakes that could impact future studies of any gene/protein of interest in heterologous expression systems.

Nontransgenic Guinea Pig Strains Exhibit Hallmarks of Human Brain Aging and Alzheimer's Disease

Older age is the primary risk factor for most chronic diseases, including Alzheimer's disease (AD). Current preclinical models to study brain aging and AD are mainly transgenic and harbor mutations intended to mirror brain pathologies associated with human brain aging/AD (eg, by increasing production of the amyloid precursor protein, amyloid beta [Aβ], and/or phosphorylated tau, all of which are key pathological mediators of AD). Although these models may provide insight on pathophysiological processes in AD, none completely recapitulate the disease and its strong age-dependence, and there has been limited success in translating preclinical results and treatments to humans. Here, we describe 2 nontransgenic guinea pig (GP) models, a standard PigmEnTed (PET) strain, and lesser-studied Dunkin-Hartley (DH) strain, that may naturally mimic key features of brain aging and AD in humans. We show that brain aging in PET GP is transcriptomically similar to human brain aging, whereas older DH brains are transcriptomically more similar to human AD. Both strains/models also exhibit increased neurofilament light chain (NFL, a marker of neuronal damage) with aging, and DH animals display greater S100 calcium-binding protein B (S100β), ionized calcium-binding adapter molecule 1 (Iba1), and Aβ and phosphorylated tau-which are all important markers of neuroinflammation-associated AD. Collectively, our results suggest that both the PET and DH GP may be useful, nontransgenic models to study brain aging and AD, respectively.

Of Humans and Gerbils— Independent Diversification of Neuroligin-4 Into X- and Y-Specific Genes in Primates and Rodents

The neural cell adhesion protein neuroligin-4 has puzzled neuroscientists and geneticist alike for almost two decades. Its clinical association with autism spectrum disorders (ASD) is well established, however, its diversification into sex chromosome-specific copies, NLGN4X and NLGN4Y, remains uncharted territory. Just recently, the presence of substantial neuroligin-4 sequence differences between humans and laboratory mice, in which Nlgn4 is a pseudoautosomal gene, could be explained as a consequence of dramatic changes affecting the pseudoautosomal region on both sex chromosomes in a subset of rodents, the clade eumuroida. In this study, we describe the presence of sex chromosome-specific copies of neuroligin-4 genes in the Mongolian gerbil (Meriones unguiculatus) marking the first encounter of its kind in rodents. Gerbils are members of the family Muridae and are closely related to mice and rats. Our results have been incorporated into an extended evolutionary analysis covering primates, rodents, lagomorphs, treeshrews and culogos comprising together the mammalian superorder euarchontoglires. We gathered evidence that substantial changes in neuroligin-4 genes have also occurred outside eumuroida in other rodent species as well as in lagomorphs. These changes feature, e.g., a general reduction of its gene size, an increase in its average GC-content as well as in the third position (GC3) of synonymous codons, and the accumulation of repetitive sequences in line with previous observations. We further show conclusively that the diversification of neuroligin-4 in sex chromosome-specific copies has happened multiple times independently during mammal evolution proving that Y-chromosomal NLGN4Y genes do not originate from a single common NLGN4Y ancestor.