Schnittker, R. R. | Search bioRxiv

bioRxiv2024

Positional information modulates transient regeneration-activated cell states during vertebrate appendage regeneration.

Injury is a common occurrence in the life of organisms. Because the extent of damage cannot be predicted, injured organisms must determine how much tissue needs to be restored. It is known that amputation position determines the regeneration speed of amputated appendages in regeneration-competent animals. Yet, it is not clear how positional information is conveyed during regeneration. Here, we investigated tissue dynamics in regenerating caudal fins in the African killifish (Nothobranchius furzeri). We report position-specific, differential modulation of the spatial distribution, duration, and magnitude of proliferation. Regenerating fins profiled by single cell RNA sequencing identified a Transient Regeneration-Activated Cell State (TRACS) that is amplified to match a given amputation position. We located this TRACS to the basal epidermis and found them to express components and modifiers of the extracellular matrix (ECM). We propose a role for these cells in transducing positional information to the regenerating blastema by remodeling the ECM. HighlightsO_LIAmputation position changes tissue-wide proliferation response C_LIO_LITranscriptional compartmentalization is relative to injury type C_LIO_LIRegeneration deploys Transient Regeneration-Activated Cell States C_LIO_LIPrediction: positional information is transduced by ECM changes during regeneration C_LI

developmental biology↗

bioRxiv2023

Post-meiotic mechanism of facultative parthenogenesis in gonochoristic whiptail lizard species.

Facultative parthenogenesis (FP) has historically been regarded as rare in vertebrates, but in recent years incidences have been reported in a growing list of fish, reptile, and bird species. Despite the increasing interest in the phenomenon, the underlying mechanism and evolutionary implications have remained unclear. A common finding across many incidences of FP is a high degree of homozygosity at microsatellite loci. This has led to the proposal that first or second polar body fusion following the meiotic divisions restores diploidy and thereby mimics fertilization. Here we show that FP occurring in the gonochoristic Aspidoscelis species A. marmoratus and A. arizonae results in genome-wide homozygosity, an observation inconsistent with polar body fusion as the underlying mechanism of restoration. Instead, a high-quality reference genome for A. marmoratus and analysis of whole-genome sequencing from multiple FP and control animals reveals that a post-meiotic mechanism gives rise to homozygous animals from haploid, unfertilized oocytes. Contrary to the widely held belief that females need to be isolated from males to undergo FP, females housed with conspecific and heterospecific males produced unfertilized eggs that underwent spontaneous development. In addition, a mixture of offspring arising from fertilized eggs and parthenogenetic development was observed to arise from a single clutch. Strikingly, our data support a mechanism for facultative parthenogenesis that removes all heterozygosity in a single generation. Complete homozygosity exposes the genetic load and explains the high rate of congenital malformations and embryonic mortality associated with FP in many species. Conversely, FP constitutes strong purifying selection as non-functional alleles of all essential genes are purged in a single generation.

genomics↗