Biology subjects

Hertel, M.

Publications and source records attributed to Hertel, M..

5 recordsLinked to original sources

bioRxiv2025

The germline-restricted chromosome orchestrates germ cell development in passerine birds

While the definition of germ cell fate has been extensively studied in model organisms, evolutionary innovations and mechanistic novelties may remain hidden in understudied systems. The phenomenon of programmed DNA elimination allows germ cells to acquire germline-restricted genes, offering a novel paradigm of germ cell specificity. In passerine birds, the germline-restricted chromosome (GRC) is eliminated from somatic cells in early embryogenesis, yet the role and consequences of its maintenance in the germ cells remain poorly understood. Here, using the zebra finch Taeniopygia guttata as a model, we combined RNA-seq and Spatial Transcriptomics to construct a high-resolution spatiotemporal expression map to understand the role of the GRC across germ cell development. We found a GRC-linked integrin-BMP signaling in maturing oocytes and tfebGRC upregulation at blastoderm embryos, suggesting the involvement of the GRC in oocyte maturation and germ cell determination. We also identified developmental specialization of GRC-linked gene expression relative to their paralogs on the autosomes and sex chromosomes, revealing a gene repertoire which promotes germline stemness and germline/soma distinction. Together, the passerine GRC constitutes a unique system that manifests germ cell complexity, whilst allowing pinpointing the effects on gene expression that may elucidate vertebrate germ cell fate.

developmental biology↗

bioRxiv2025

Integrin promotes basement membrane crossing and branching of an invading intracellular tube

The narrowest biological tubes are comprised of cells that hollow to form an intracellular lumen. Here, we examine early lumenogenesis of the C. elegans excretory cell, which branches to form an H-shaped intracellular tube spanning the length of the worm. Using genetically paralyzed embryos to freeze movement, we describe lumen initiation and branching for the first time using time-lapse fluorescence microscopy. We show that the excretory cell lumen forms through a plasma membrane invasion mechanism when a nascent lumen grows from the plasma membrane into the cytoplasm. The lumen subsequently extends along the left-right axis before branching to form anterior-posterior projections. Through a genetic screen, we identify mutations in ina-1/-integrin and pat-3/{beta}-integrin that block lumenogenesis at the anterior-posterior branching step, and we show that integrin function is required within the excretory cell. Finally, we find that the excretory cell crosses the epidermal basement membrane where anterior-posterior branches form and demonstrate that basement membrane crossing fails in integrin mutant embryos. Our findings reveal how an intracellular lumen initiates and branches and identify integrins and basement membrane as key branching regulators.

developmental biology↗

bioRxiv2022

GO WIDE TO GO DEEP: AFFORDABLE, REPLICABLE ROBOTIC MINIRHIZOTRON SAMPLING FOR PHENOLOGY STUDIES

Automating dynamic fine root data collection in the field is a longstanding challenge with multiple applications for co-interpretation and synthesis for ecosystem understanding. High frequency root data are only achievable with paired automated sampling and processing. However, automatic minirhizotron (root camera) instruments are still rare and data is often not collected in natural soils nor analysed at high temporal resolution. Instruments must also be affordable for replication and robust under variable natural conditions. Here, we show a system built with off-the-shelf parts which samples at sub-daily resolution. We paired this with a neural network to analyse all images collected. We performed two mesocosm studies and two field trials alongside ancillary data collection (soil CO2 efflux, temperature and moisture content, and PhenoCam-derived above-ground dynamics. We produce robust daily time-series of root dynamics under all conditions. Temporal root changes were a stronger driver than absolute biomass on soil CO2 efflux in mesocosm. Proximal sensed above ground dynamics and belowground from minirhizotron data were not synchronised. Root properties extracted were sensitive to soil moisture and occasionally to time of day (potentially relating to soil moisture). This may only affect high frequency imagery and should be considered in interpreting such data. HIGHLIGHTCompletely automatic root dynamics with method transferrable between field settings.

ecology↗

bioRxiv2021

Occasional paternal inheritance of the germline-restricted chromosome in songbirds

All songbirds have one special accessory chromosome1-4, the so-called germline-restricted chromosome (GRC)4-7, which is only present in germline cells and absent from all somatic tissues. Earlier work on the zebra finch (Taeniopygia guttata castanotis) showed that the GRC is inherited only through the female line4,6,8,9 - like mitochondrial DNA7,9-12 - and is eliminated from the sperm during spermatogenesis5,7,9-11. Here we show that the GRC can also be paternally inherited. Confocal microscopy using GRC-specific FISH probes indicated that a considerable fraction of sperm heads (1-19%) in zebra finch ejaculates still contained the GRC. In line with these cytogenetic data, sequencing of ejaculates revealed that individual males from two families differed strongly and consistently in the number of GRCs in their ejaculates. Examining a captive-bred population of hybrids of the two zebra finch subspecies (T. g. guttata and T. g. castanotis) revealed that the descendants inherited their mitochondria from a castanotis mother but their GRC from a guttata father. Moreover, GRC haplotypes across nine different castanotis matrilines showed at best a weak tendency to be co-inherited with mtDNA haplotypes. Within castanotis, the GRC showed little variability, while the mtDNA of matrilines was highly divergent. This suggests that a single GRC haplotype has recently spread across the entire castanotis population, crossing the matriline boundaries via paternal spillover. Our findings raise the possibility that certain GRC haplotypes could selfishly spread through the population, via additional paternal transmission, thereby outcompeting other GRC haplotypes that were limited to strict maternal inheritance, even if this was partly detrimental to organismal fitness.

genomics↗

bioRxiv2020

Highly efficient genome modification of cultured primordial germ cells with lentiviral vectors to generate transgenic songbirds

SUMARYThe ability to genetically manipulate organisms has led to significant insights in functional genomics in many species. In birds, manipulation of the genome is hindered by the inaccessibility of the one-cell embryo. During embryonic development, avian primordial germ cells (PGCs) migrate through the blood stream and reach the gonadal anlage; where they develop into mature germ cells. Here, we explored the use of PGCs to produce transgenic offspring in the zebra finch, which is a major animal model for sexual brain differentiation, vocal learning and vocal communication. Zebra finch PGCs (zfPGCs) obtained from embryonic blood significantly proliferated when cultured in an optimized culture medium and conserved the expression of germ and stem cell markers. Transduction of cultured zfPGCs with lentiviral vectors was highly efficient leading to strong expression of the enhanced green fluorescent protein (eGFP). Transduced zfPGCs were injected into the host embryo and transgenic songbirds were successfully generated.

neuroscience↗