Phenotypes of mice with deletions of individual genes within this interlocked feedback loop are mild; however, deletion of both Rev-Erbα and Rev-Erbβ genes disrupts circadian rhythms, demonstrating that cyclical repression at RORE and REV-Re elements by the REV-ERB proteins represents a critical component of circadian timekeeping.
Moreover, active histone marks across the Scl locus were significantly reduced in Scl Δ19/Δ19 fetal liver cells without major changes in steady-state messenger RNA levels, suggesting post-transcriptional compensation for loss of a regulatory element, a result that might be widely relevant given the frequent observation of mild phenotypes after deletion of regulatory elements.
For the genes used in this activity, the RNAi phenotypes were similar to, but usually milder than, the deletion strain phenotypes.
Comparing genotype with ocular findings, severe ocular abnormalities were associated with large 4p deletions while mild ocular disorders were independent of the deletion size [ 61].
The observation of relatively mild phenotypes after the deletion of regulatory elements is a common finding.
The prevalence of intellectual disability is also high, with 31% of children with the deletion having mild intellectual disability.
Furthermore, the mild effect of Cfp1 deletion on Pol II binding at most promoters is in strong contrast to the observation at the promoter of Jade-1.
Notably, several groups have observed mild anemic phenotypes with deletion of the abbreviated miR-144/451 locus in mice, yet these studies did not take into account potential regulatory factors flanking this site [ 31, 58].
In a comparison to two domestic chicken genomes and the Gallus gallus reference genome, we found no unique mutational processes shaping the DT40 genome except for a mild increase in insertion and deletion events, particularly deletions at tandem repeats.
However, when compared to the excessive neuronal differentiation caused by Dll1 mutation in the V0 and V2 domains, the V1 neurogenic phenotype due to Jag1 deletion is milder and seems to be rescued at later stages, as two V1-derived subtypes of INs are produced in normal numbers in Jag1 mutants.
