In the nematode Caenorhabditis elegans, germ cells arise from early embryonic cells called germline blastomeres. Cytoplasmic structures called P granules are present in the fertilized egg and are segregated into each of the germline blastomeres during the first few cleavages of the embryo. Mutations in the maternally expressed gene mex-1 disrupt the segregation of P granules, prevent the formation of germ cells, and cause inappropriate patterns of somatic cell differentiation. We have cloned the mex-1 gene and determined the distribution pattern of the mex-1 gene products. The MEX-1 protein contains two copies of an unusual ‘finger’ domain also found in the PIE-1 protein of C. elegans. PIE-1 has been shown to be expressed in germline blastomeres, and is a component of P granules. We show here that MEX-1 also is present in germline blastomeres and is a P granule component, although MEX-1 is a cytoplasmic protein while PIE-1 is present in both the nucleus and cytoplasm. We further show that MEX-1 is required to restrict PIE-1 expression and activity to the germline blastomeres during the early embryonic cleavages.
REFERENCES
Barstead
R. J.
, Waterson
R. H.
(1991
) Vinculin is essential for muscle formation in the nematode.
J. Cell Biol
114
, 715
–724
Bowerman
B.
, Eaton
B. A.
, Priess
J. R.
(1992
) skn-1, a maternally expressed gene required to specify the fate of ventral blastomeres in the early C. elegans embryo.
Cell
68
, 1061
–1075
Bowerman
B.
, Draper
B. W.
, Mello
C. M.
, Priess
J. R.
(1993
) The Maternal gene skn-1 encodes a protein that is distributed unequally in early C. elegans embryos.
Cell
74
, 443
–452
Boyd
L.
, Guo
S.
, Levitan
D.
, Stinchcomb
D.
, Kemphues
K. J.
(1996
) PAR-2 is asymmetrically distributed and promotes association of P granules and PAR-1 with the cortex in C. elegans embryos.
Development
122
, 3075
–3084
Brenner
S.
(1974
) The genetics of Caenorhabditis elegans.
Genetics
77
, 71
–94
Draper
B. W.
, Mello
C. C.
, Bowerman
B.
, Hardin
J.
, Priess
J. R.
(1996
) MEX-3 is a KH domain protein that regulates blastomere identity in early C. elegans embryos.
Cell
87
, 205
–216
Dubois
R. N.
, McLane
M.
, Ryder
K.
, Lau
L. F.
, Nathans
D.
(1990
) A growth factor-inducible nuclear protein with a novel cystein/histidine repetitive sequence.
J. Biol. Chem
265
, 19185
–19191
Guo
S.
, Kemphues
K. J.
(1995
) par-1, a gene required for establishing polarity in C. elegans embryos, encodes a putative Ser/Thr kinase that is asymmetrically distributed.
Cell
81
, 611
–620
Herschman
H. R.
, Kujubu
D. A.
, Fletcher
B. S.
, Ma
Q.
, Varnum
B. C.
, Gilbert
R. S.
, Reddy
S. T.
(1994
) The tis genes, primary response genes induced by growth factors and tumor promoters in 3T3 cells.
Prog. Nucl. Acid Res. and Mol. Biol
47
, 113
–149
Hiraoka
Y.
, Swedlow
J. R.
, Paddy
M. R.
, Agard
D. A.
, Sedat
J. W.
(1991
) Three-dimensional multiple-wavelength fluorescence microscopy for the structural analysis of biological phenomena.
Sem. Cell Biol
2
, 153
–165
Hird
S. N.
, Paulsen
J. E.
, Strome
S.
(1996
) Segregation of germ granules in living Caenorhabditis elegans embryos: cell-type-specific mechanisms for cytoplasmic localisation.
Development
122
, 1303
–1312
Hunter
C. P.
, Kenyon
C.
(1996
) Spatial and temporal controls target pal-1 blastomere-specification activity to a single blastomere lineage in C. elegans embryos.
Cell
87
, 217
–226
Kemphues
K. J.
, Kusch
M.
, Wolf
N.
(1988
) Maternal-effect lethal mutations on linkage group II of Caenorhabditis elegans.
Genetics
20
, 977
–986
Krause
M.
, Hirsh
D.
(1987
) A trans-spliced leader sequence on actin mRNA in C. elegans
Cell
49
, 753
–761
Lin
R.
, Thompson
S.
, Priess
J. R.
(1995
) pop-1 encodes an HMG box protein required for specification of a mesodermal precursor in early C. elegans embryos.
Cell
83
, 599
–609
Ma
Q.
, Wadleigh
D.
, Chi
T.
, Herschman
H. R.
(1994
) The Drosophila TIS11 homologue encodes a developmentally controlled gene.
Oncogene
9
, 3329
–3334
Ma
Q.
, Herschman
H. R.
(1995
) The yeast homologue YTIS11, of the mammalian TIS11 gene family is a non-essential, glucose repressible gene.
Oncogene
10
, 487
–494
Mello
C.
, Kramer
L. M.
, Stinchcomb
D.
, Ambros
V.
(1991
) Efficient gene transfer in C. elegans: extrachromosomal maintenance and integration of transforming sequences.
EMBO J
10
, 3959
–3970
Mello
C. C.
, Draper
B. W.
, Krause
M.
, Weintraub
H.
, Priess
J. R.
(1992
) The pie-1 and mex-1 genes and maternal control of blastomere identity in early C. elegans embryos.
Cell
70
, 163
–176
Mello
C. C.
, Schubert
C.
, Draper
B. W.
, Zhang
W.
, Lobel
B.
, Priess
J. R.
(1996
) Dynamic localization of PIE-1, a maternally encoded protein required for the germ cell fate in early C. elegans embryos.
Nature
382
, 710
–712
Robinson
P. A.
, Anderton
B. H.
, Loviny
T. L. F.
(1988
) Nitrocellulose-bound antigen repeatedly used for the affinity purification of specific polyclonal antibodies for screening DNA expression libraries.
J. Immunol. Meth
108
, 115
–122
Schnabel
R.
, Weigner
C.
, Hutter
H.
, Feichtinger
R.
, Schnabel
H.
(1996
) mex-1 and the general partitioning of cell fate in the early C. elegans embryo. Mech.
Dev
54
, 133
–147
Seydoux
G.
, Fire
A.
(1994
) Soma-germline asymmetry in the distributions of embryonic RNAs in Caenorhabditis elegans.
Development
120
, 2823
–2834
Seydoux
G.
, Mello
C. C.
, Pettitt
J.
, Wood
W. B.
, Priess
J. R.
, Fire
A.
(1996
) Repression of gene expression in the embryonic lineage of C. elegans
Nature
382
, 713
–716
Spieth
J.
, Brooke
G.
, Kuersten
S.
, Lea
K.
, Blumenthal
T.
(1993
) Operons in C. elegans: Polycistronic mRNA precursors are processed by trans-splicing of SL2 to downstream coding regions.
Cell
73
, 521
–532
Strome
S.
, Wood
W. B.
(1983
) Generation of asymmetry and segregation of germ-line granules in early C. elegans embryos.
Cell
35
, 15
–25
Sulston
J. E.
, Schierenberg
E.
, White
J. G.
, Thomson
J. N.
(1983
) The embryonic cell lineage of the nematode Caenorhabditis elegans.
Dev. Biol
100
, 64
–119
Varnum
B. C.
, Lim
R. W.
, Sukhatme
V. P.
, Herschman
H. R.
(1989
) Nucleotide sequence of a cDNA encoding TIS11, a message induced in Swiss 3T3 cells by the tumor promoter tetradecanoyl phorbol acetate.
Oncogene
4
, 119
–120
This content is only available via PDF.
© 1997 by Company of Biologists
1997
