Table 1

Expression and function of vasa homologs*

Species

Gene

RNA expression

RNA localization

Protein expression

Protein localization

Function

References


Fruit fly (Drosophila melanogaster)

vasa

Early embryo: uniform, followed by specific expression in germ cells. Ovary: uniform in nurse cells and oocyte. Testis: early stage spermatocytes and germline stem cells.

No

Germ cells: as soon as they form and throughout embryonic development. Ovary: germline stem cells, nurse cells, oocytes. Testis: early stages of spermatogenesis.

Oocyte and cleavage-stage embryos: in polar granules, nuclear bodies and dense cytoplasmic masses.

Early embryogenesis: abdomen development, nanos mRNA translation, formation of pole plasm and germ cells. Oogenesis: germline cyst development, oocyte differentiation, gurken mRNA translation, oocyte polarity, translation of oskar mRNA.

[13,14,16,17,40,41]

Mouse (Mus musculus)

Mvh

Testis: spermatocytes and early spermatids. Ovary: ND

No

Germ cells: as they arrive at thethe genital ridge. Ovary: early stages of oogenesis. Decreases during maturation. Not detected in mature oocytes. Testis: in spermatogonium to round spermatid stages.

Granules near nucleus in pachytene-diplotene spermatocytes. After meiosis: a large perinuclear granule up to spermatid nucleus elongation. Sperm: corresponds to that of the 'chromatoid body'.

Testis: required in PGCs during premeiotic stages of spermatogenesis for sperm differentiation before pachytene spermatocyte stage. Male mutants: PGC proliferation defects. Female mutants: fertile and show no defects of oogenesis.

[19,20,38]

Zebrafish (Danio rerio)

vasa

Maternally supplied to embryo. From the 32-cell stage, detected in four blastomeres. Gastrulation: expressed in four PGC clusters as they migrate towards the gonad. Testis: spermatogenesis, excluding mature spermatozoa. Ovary: all stages of oogenesis.

One-cell embryo: ring between yolk and cytoplasm. Two- to four-cell embryo: near cleavage furrow, inherited by four cells. Then asymmetrically localized and distributed between dividing blastomeres until late blastula, when it fills PGCs' cytoplasm. Late oogenesis: oocyte cortex.

Maternal protein uniformly distributed during blastula stages. At late blastula, distinct expression in PGCs as expression in somatic cells decreases.

Associated with germinal vesicle in early oogenesis. From late blastula on, associated with nuclear envelope in a pattern distinct from that of the RNA.

ND

[6,9,23,31]

Planarian (Dugesia japonica)

DjvlgA, DjvlgB

Testis: DjvlgA in spermatogonia, spermatocytes, spermatids. DjvlgB only in spermatocytes. Ovary: both expressed in oocytes. Outside gonad DjvlgA expressed in totipotent neoblasts.

No

ND

ND

ND

[26]

Frog (Xenopus laevis)

XVLG1

Gonad in both sexes. Ovary: all stages of oogenesis. Gastrulation: PGC-specific expression.

No

Oocytes and unfertilized eggs. Blastula and gastrula: all cells, intensity of staining decreasing with time. After gastrulation: level increases in PGCs.

Embryos: appears to be perinuclear.

Survival or differentiation of PGCs. [22,42,43,44]

Chick (Gallus gallus)

Cvh

Testis: spermatogonia to mature spermatocytes. Ovary: ND

ND

Embryos: maternal protein from the one-cell stage. Before gastrulation: Cvh-positive PGCs in center of area pellucida. Migrating and post-migratory PGCs. Testis: spermatogonia to round spermatids. Ovary: immature oocytes.

Cleaving embryos: basal part of cleavage furrows.Testis: granular staining in spermatocytes. Ovary: underneath plasma membrane, near germ-plasm-associated organelles and molecules such as mitochondria and spectrin.

ND

[8]

Ascidian (Ciona intestinalis)

Ci-DEAD1

Embryo: mesenchymal cells and posterior cells presumed to be germ cells. Ovary: early oogonic cells. Testis: early spermatogenic cells.

Early embryos: posterior during two- to four-cell stage, inherited by presumed germ cells.

ND

ND

ND

[27]

Nematode (Caenorhabditis elegans)

glh-1, glh-2, glh-3, glh-4

glh-1, glh-2, glh-3 and glh-4 expressed in all cells of early cleavage stages followed by a decrease to background levels. All expressed in germline cells in male and hermaphrodite.

No

All expressed throughout life, first in germline blastomeres and later in germ cells in gonad.

All localized to P-granules that segregate to germline blastomeres. Granules are cytoplasmic in oocyte and early embryo and perinuclear at later stages.

G1h-1, g1h-2 and g1h-4 products are required for germ-cell proliferation and gametogenesis. Oogenesis and spermatogenesis defective in glh-1/4(RNAi), with many cells not proceeding beyond pachytene.

[28,45]

Human (Homo sapiens)

VASA

In the fetus and adult, gonad-specific expression in both sexes.

ND

Germ cells: expressed in PGCs as they populate the gonadal ridge as well as in PGCs that have not yet reached this target. Testis: spermatogonia, spermatocysts and spermatids. Ovary: oocytes.

Testis: granular staining in spermatocytes. Ovary: in fetal oocytes: within a compact perinuclear body. In adult oocytes no subcellular localization.

ND: hereditary infertility syndromes that map to the chromosomal region of VASA have not yet been found.

[30]


*Not all the known vasa homologs are listed in the table. Homologs for which little functional information is available have been omitted unless they shed light on the function of the gene in a certain class of organism. ND, not determined.

Raz Genome Biology 2000 1:reviews1017.1-reviews1017.6   doi:10.1186/gb-2000-1-3-reviews1017