Table 1.

Gene expression variability of different functional gene categories

Gene category 1	Gene category 2	Difference in adjusted mean expression variability (log10 F-statistic)
		Category 1 – category 2	95 % CI	p value
Ion channel	Metabolism	0.32	0.22–0.41	<10−5
Ion channel	Ribosome	0.33	0.23–0.42	<10−5
Ion channel	Transcription factor	0.16	0.07–0.25	4.84 × 10−5
Transcription factor	Metabolism	0.16	0.11–0.20	<10−5
Transcription factor	Ribosome	0.17	0.12–0.22	<10−5
Ribosome	Metabolism	−0.01	−0.06–0.04	0.92

Comparison of gene expression variability across functional gene categories controlling for gene expression level. Adjusted mean values were calculated using a two-factor ANCOVA of log₁₀ F-statistic, with functional gene category and cell type as independent factors and conditioning on gene expression level (log₁₀ average normalized read depth). Adjusted means are reported at the average gene expression level. Reported p values are for a two-sided Tukey’s test and are calculated based on a joint t-distribution to control the family-wise error rate