From egg to pole cells: Ultrastructural aspects of early cleavage and germ cell determination in insects

Zissler, Dieter

doi:10.1002/jemt.1070220106

Cited by 29 publications

(19 citation statements)

References 121 publications

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“…Therefore hymenopteran oocytes utilize AN for distributing snRNPs, centrosomal proteins, and possibly some other factors of maternal origin to the cortical region, where they are needed during initial stages of embryonic development. In most insects, early embryonic stages of development are confined to the cortical region of the egg (the superficial cleavage) and it is here where the blastoderm forms (1), massive transcriptional activity of blastoderm nuclei starts (2), and blastoderm cells intensively multiply by mitotic divisions (3) (reviewed in Zissler, 1992;Buning, 1994). Thus the accumulation of snRNPs and γ-tubulin in the cortical region of the oocyte might be directly linked to the intensity of these processes.…”

Section: Biogenesis Of Small Nuclear Ribonucleoproteinsmentioning

confidence: 99%

Accessory nuclei in insect oogenesis: in search of the function of enigmatic organelles

Jaglarz¹,

Kloc²,

Biliński³

2008

Int. J. Dev. Biol.

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This review compiles present knowledge of the structure and molecular composition of the enigmatic cytoplasmic organelles called accessory nuclei. Most typically, they are found in the perinuclear cytoplasm in oocytes of insects and several other invertebrates. Accessory nuclei originate by budding of the oocyte nucleus (germinal vesicle) and are surrounded by an enelope identical to the nuclear envelope. They contain one or several dense inclusions called pseudonucleoli immersed in a translucent ground substance or matrix. Comparative analysis of the morphology, molecular composition and the ultimate fate of accessory nuclei and their inclusions revealed that there are two basic types of these organelles in insect oocytes. In mallophagans, accessory nuclei are associated with the oocyte nucleus throughout entire oogenesis and at least some of them are connected to the germinal vesicle by slender stems. Each accessory nucleus contains a single, dense, RNA-positive inclusion which is likely to correspond to a nucleolus. In hymenopterans, accessory nuclei initially surround the germinal vesicle but during oogenesis they separate from it and migrate toward the peripheral ooplasm. Within the accessory nucleus matrix usually two distinct inclusions develop. One of these is perfectly spherical, contains coilin and small nuclear ribonucleoproteins and is homologous to the Cajal body. In the light of recent discoveries, we discuss the role accessory nuclei play in insect oogenesis and early embryogenesis.

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Section: Biogenesis Of Small Nuclear Ribonucleoproteinsmentioning

confidence: 99%

Accessory nuclei in insect oogenesis: in search of the function of enigmatic organelles

Jaglarz¹,

Kloc²,

Biliński³

2008

Int. J. Dev. Biol.

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“…Among the holometabolous insects, the presence of distinct germ plasm and the early segregation of germline precursors seems to be widespread, though not ubiquitous (Eddy, 1975;Nieukoop and Sutasurya, 1981;Zissler, 1992). However, the situation among hemimetabolous insects is highly variable.…”

Section: Introductionmentioning

confidence: 96%

Germ Line Development in the Grasshopper Schistocerca gregaria: vasa As a Marker

Chang¹,

Dearden²,

Akam³

2002

Developmental Biology

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Vasa is a widely conserved germline marker, both in vertebrates and invertebrates. We identify a vasa orthologue, Sgvasa, and use it to study germline development in the grasshopper Schistocerca gregaria, a species in which no germ plasm has been identified. In adults, Sgvasa is specifically expressed in the ovary and testis. It is expressed at high levels during early oogenesis, but no detectable vasa RNA and little Vasa protein are present in mature unlaid eggs. None appears to be localized to any defined region of the egg cortex, suggesting that germline specification may not depend on maternal germ plasm expressing vasa. Vasa protein is expressed in most cleavage energids as they reach the egg surface and persists at high levels in most cells aggregating to form the embryonic primordium. However, after gastrulation, Vasa protein persists only in extraembryonic membranes and in cells at the outer margin of the late heart-stage embryo. In the embryo, it then become restricted to cells at the dorsal margin of the forming abdomen. In older embryos, these Vasa-positive cells move toward the midline; Vasa protein accumulates asymmetrically in their cytoplasm, a pattern closely resembling that of germ cells in late embryonic gonads. Thus, we suggest that the Vasa-stained cells in the abdominal margin are germ cells, as proposed by Nelson (1934), and not cardioblasts, as has been proposed by others.

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“…Many arthropod eggs are centrolecithal. Centrolecithal zygotes undergo meroblastic cleavage, where the cleavage plane extends only to the accumulated yolk and is superficial [11]. Direction of cell fates with nutrient gradient can only occur later after asymmetrical allocation of the generated cell nuclei, after which there leads to partial differentiation in gastrulation.…”

Section: Nutrient Gradient As Generally Formed To Partially Differentmentioning

confidence: 99%

Regulation of Both Cell State and Gene Expression with Nutrient Gradient as Conserved Mechanism Differentiating the Cell Fates for Embryonic Gastrulation: A Theory

Cai¹

2016

OALib

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In this article, it is newly suggested the regulation from nutrient gradient on both cell metabolic state and expressional gene classes as the conserved mechanism differentiating the cell fates for formation of the three germ layers of gastrula in animals. As a new theory, it is supported by the totipotency and pluripotency of early embryonic cells and cultured stem cells to be regulated by nutrients, as well as by the universal formation of nutrient gradient during gastrulation in various animals. Besides, it is also supported by the subsequent phenotypic fates of three germ layers of gastrula, with the endoderm manifesting expression of gene classes in nutritious condition and giving rise to the epithelium of digestive and respiratory system; the ectoderm manifesting expression of gene classes with nutrient dependence and environmental effect, and giving rise to the nervous and epithelial tissues; the mesoderm lying between them and giving rise to the muscle and adipose. Likewise, it is directly supported by the different nutrient effects onto such trilaminar differentiation in various cultured stem cells. Finally, it is in further supported by the evolutionary effects of nutrients in preserving the trilaminar fates in gastrula versus relative permitting the variations in anteroposterior determination. Conclusively, it is identified the nutrient gradient as an important mechanism to partially differentiate the cell fates for embryonic gastrulation.

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From egg to pole cells: Ultrastructural aspects of early cleavage and germ cell determination in insects

Cited by 29 publications

References 121 publications

Accessory nuclei in insect oogenesis: in search of the function of enigmatic organelles

Accessory nuclei in insect oogenesis: in search of the function of enigmatic organelles

Germ Line Development in the Grasshopper Schistocerca gregaria: vasa As a Marker

Regulation of Both Cell State and Gene Expression with Nutrient Gradient as Conserved Mechanism Differentiating the Cell Fates for Embryonic Gastrulation: A Theory

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