Worm Breeder's Gazette 11(3): 49

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

unc-86 Protein: Location in Time, Space and Cell Lineage

Michael Finney and Gary Ruvkun

Figure 1

Figure 2

unc-86 mutations affect the cell identities of specific neurons and 
neuroblasts.  To investigate how the gene acts at the molecular and 
cellular levels, we made antibodies to the unc-86 protein.  In brief.  
we made a full-length cDNA clone using PCR, expressed it in E.  coli, 
purified the protein, and immunized rabbits.  Affinity-purified sera 
stain nuclei in wild-type animals but not in unc-86 deletion mutants.
The antisera stain the nuclei of 47 neurons in a newly-hatched L1 
and 57 neurons in adults.  Most of these neurons have been identified 
at least tentatively.  The anterior nerve ring identifications are by 
Cori Bargmann.  All of the cells that are known to be affected by unc-
86 stain, with the exception of SDQR/L (see below).
[See Figure 1]
As shown below, in unc-86 mutants the QR and QL lineages are 
transformed such that one daughter, Q.p, seems to have the same 
identity as its mother instead of its normal identity.  We have 
investigated where and when in the Q lineages unc-86 protein is 
expressed.  We first see unc-86 protein in QX.p; the staining is 
unclear but becomes cytoplasmic during mitoses.  The protein is 
distributed to the descendents of QX.p.  QX.pp dies, still containing 
unc-86 protein; in ced-3 animals, there is an extra staining nucleus 
where the cell death survivor should be.  One cell, AVM/PVM, continues 
to contain unc-86 protein in its nucleus into adulthood.  The third 
cell, SDQR/L, contains unc-86 protein at birth but quickly degrades it.
Unexpectedly, a descendent of QX.a, AQR/PQR, begins to express unc-
86 protein even though none of its ancestors did.
These data and similar data for the post-dereid neuroblast suggest 
that in lineages the expression of unc-86 protein in certain daughter 
cells alters what would otherwise be a stem-cell-like lineage by 
making the cell identity of that daughter different from the cell 
identity of the mother.  Models in which unc-86 acts non-autonomously 
or in which the mother/daughter asymmetry results from segregation of 
the unc-86 protein at cell divisions are now considered unlikely.
[See Figure 2]

Figure 1

Figure 2