Table 1.

Average ± SEM number of clones per coverslip

Clone type	Control	PDGF	CNTF	CNTF + PDGF	CNTF → PDGF	PDGF → CNTF
Neuron	2.9  ± 0.9	6.6  ± 1.7	2.7  ± 0.2	4.0  ± 0.0	5.1  ± 0.8	5.4  ± 1.3
Astrocyte	0	0.1  ± 0.1	2.6  ± 0.4	1.1  ± 0.7	0.3  ± 0.3	0.3  ± 0.4
NE	5.0  ± 2.0	0.8  ± 0.6	1.4  ± 0.3	0.6  ± 0.1	0.5  ± 0.3	0.4  ± 0.4
Mixed	0	0.4  ± 0.4	1.9  ± 0.8	1.1  ± 0.7	1.0  ± 0.8	0.5  ± 10
Total β-gal+ clones per coverslip	7.9  ± 1.1	7.9  ± 1.9	8.6  ± 0.5	6.8  ± 0.1	6.9  ± 1.5	6.6  ± 2.0

Clonal analysis of CNTF and PDGF stimulated cells. Single NE cells respond asymmetrically to CNTF and PDGF. E14 NE cultures were infected with the β-gal retrovirus as described previously (Williams et al., 1997) and then treated with PDGF BB, CNTF, CNTF and PDGF simultaneously, CNTF followed by PDGF, or PDGF followed by CNTF. In all cases (single, simultaneous, or sequential treatment), growth factors were used at a final concentration of 30 ng/ml for 4 hr. After growth factor(s) treatment, cultures were washed and grown in factor-free media for an additional 5 d. The composition of β-gal-positive clones was then analyzed. Neurons were identified using anti-TuJ1, astrocytes were identified using anti-GFAP, and NE cells were identified as cells labeling with anti-nestin antibody but not with antibodies that recognize differentiated cell types (Williams et al., 1997). Mixed clones refer to clones composed of astrocytes, neurons, and NE cells. Results shown are the mean ± SEM of three separate experiments. Relative to CNTF alone, the decrease in astrocyte clones caused by PDGF added at the same time (CNTF + PDGF), after (CNTF → PDGF), or before (PDGF → CNTF) exposure to CNTF is significant (p = 0.01, 0.05, and 0.005, respectively). Conversely, the increase in neuronal clones under the same conditions is significant (p = 0.01, 0.001, and 0.05, respectively).