Since intron density is high in broadly expressed genes [ 25], the relation between expression level and codon usage may be explained by effects owing to splice regulation.
Broadly expressed human genes would be more compact than narrowly expressed ones in consequence of the high correlation between expression level and breadth.
In our case, the observed correlation between expression level and variance (Kendall's rank correlation test τ = 0.887, P value <2.2 × 10−16) was removed when using a polynomial regression of the third degree to estimate log (σ2).
These SiLAD data adequately demonstrated that the protein dynamic changes have huge differences between expression level and total amount level.
However, to test the hypothetical correlation between expression level and phenotypic effects would require specific experiments with a larger number of GM lines as used here.
Other reports found a negative relationship between expression level and gene length and the interpretation was that there is selection pressure for highly expressed genes to remain small.
We also investigated the relationship between expression level and gene copy number of variants IV and V in the testes of 129Sv/C57BL-6J hybrid mice.
For three of the 16 pseudogenes the correlation between expression level and the intron expression statistic was nominally significant (α = 0.05).
As a consequence, proteins bearing a higher degree of polymorphisms (including balancers) may tend to be more flexible in quantitative changes, whereas cell line-specific proteins may require a stronger connection between expression level and function.
Is there a correlation between expression level and the slope?
The difference between expression level and transcript abundance remains unclear.
