Germ Cell Specification: The Evolution of a Recipe to Make Germ Cells

Abstract

Multicellular species use gametes for their propagation. Gametes are formed from primordial germ cells (PGCs), which develop during embryogenesis. In some species, PGCs are speciied by the inheritance of a RNA granule known as germ plasm. During germ cell speciication, the germ plasm conveys a unique set of properties, e.g. the germ cell speciic meiotic cell cycle to the PGCs. Germ plasm assembly is controlled by independently evolving organizer proteins like Oskar in Drosophila or Bucky ball in zebraish. These organizers are intrinsically disordered proteins, which rapidly changed their amino acid sequence during evolution. A common recipe has emerged by studies on organizer proteins for animals that use germ plasm to specify their germline. Investigating the nature of these organizers might therefore provide a clue to germ cell speciication in other species, which are less accessible to molecular-genetic and embryological approaches. Moreover, we might understand how the irst metazoans modiied their existing cellular structures from unicellular eukaryotes to ensure their reproduction.

Evolving Role of RING1 and YY1 Binding Protein in the Regulation of Germ-Cell-Specific Transcription

“…There are two basic ways of the germ cell differentiation process: preformation and epigenesis [24,25,26,27]. In the case of preformation, which is the “inherited”, or deterministic way of germ cell determination, microscopically detectable, asymmetrically localized RNA-protein granules are found in the fertilized egg.…”

Primordial Germ Cell Specification in Vertebrate Embryos: Phylogenetic Distribution and Conserved Molecular Features of Preformation and Induction

“…We also examine the distribution of PGC determination systems across diverse animal lineages, which provides further insights into how such systems may change over evolutionary time while still maintaining the ability to initiate the germline specification program. Indeed, many of the key unresolved questions remaining in the PGC specification field concern the evolutionary history of preformation and inductive mechanisms and are topics of active debate within the research community ( Swartz and Wessel, 2015 ; Whittle and Extavour, 2017 ; Krishnakumar and Dosch, 2018 ; Tan and Tee, 2019 ); for example: (1) What is the underlying reason for the conserved feature of perinuclear germ granules that may help specify the PGC gene expression program? This feature likely reflects a key aspect of germ cell specification that links biophysical features of germ cell ribonucleoparticles, overall cellular structure involving the cytoplasmic-nuclear interphase, and gene expression programs; (2) How do germ plasm components, individually and/or collectively, help initiate PGC specification, if this is indeed the case?…”

Bucky Ball Is a Novel Zebrafish Vasa ATPase Activator

“…The germline is an essential feature of life that ensures the perpetuation and survival of a species by passing the genetic information from one generation to the next by specialized germ cells [1][2][3]. In many metazoan organisms, primordial germ cells (PGCs) are segregated from somatic cells during early embryonic development [4]. In mammals such as, mice and humans, a subset of pluripotent embryonic cells is specified to PGCs by cell-cell communication (induction mode) through zygotic signaling molecules [1,[4][5][6][7][8].…”

“…In many metazoan organisms, primordial germ cells (PGCs) are segregated from somatic cells during early embryonic development [4]. In mammals such as, mice and humans, a subset of pluripotent embryonic cells is specified to PGCs by cell-cell communication (induction mode) through zygotic signaling molecules [1,[4][5][6][7][8]. Non-mammalian species such as Drosophila, C. elegans, Xenopus, and zebrafish require a specialized maternal cytoplasm referred to as germplasm to form PGCs (inherited mode) [9].…”

“…Non-mammalian species such as Drosophila, C. elegans, Xenopus, and zebrafish require a specialized maternal cytoplasm referred to as germplasm to form PGCs (inherited mode) [9]. The germplasm is inherited by a set of blastomeres to change their fate into PGCs [1,[4][5][6][7][8]. Studies carried out on the ablation, transplantation, and mislocalization of germplasm during embryonic development have revealed that germplasm is sufficient and necessary for the formation of PGCs in Xenopus, Drosophila, and zebrafish [10][11][12][13][14][15].…”