Katagiri proposes an "averaging" general linear model for multi-gene (combinatorial null mutant) systems, arguing the standard additive ANOVA model fails in three ways: mutant-allele framing obscures mechanism, a limited phenotypic range violates the distributive law ((A+B):C = A:C + B:C), and higher-order additive interaction errors propagate upward. The averaging model defines each interaction as the deviation of a genotype from the mean of all genotypes with one fewer wild-type allele (e.g., A;B;C = ABC β (AB + AC + BC)/3), keeping estimate dispersion consistent across orders .
Key supporting evidence: (1) simulation over 10,000 repeats of a 7-gene, 128-genotype system (E1); (2) in the real 4-gene Arabidopsis immunity data, omitting the 4-gene term substantially shifted additive 3-gene estimates but was "almost unnoticeable" in the averaging model (E2); (3) reanalysis revealed a strongly positive J;S interaction in ETI but not PTI, and a strongly positive P;S interaction in PTI (E3), with J dropped from elf18-PTI after significance testing (E4) .
Strengths: mathematically self-consistent derivation from algebraic laws; full reproducibility package (raw counts, model matrices, R script); honest limitation discussion (linearity assumption, possible failure of the averaging principle under strong mid-range non-linearity). Weaknesses: biological validation is a single Arabidopsis 4-gene dataset reanalyzed from the author's own prior work, creating self-confirmation risk; simulations use uniformly random phenotypes rather than structured biological networks, which may overstate additive-model failure; the "averaging principle" is a pragmatic fix for non-associativity rather than a mechanistic derivation, and interaction estimates depend on including only significant genes (a data-dependent model-selection step without multiplicity correction for gene selection). Notably, the finding that higher-order interactions explain little variance in mapping populations does not directly test the averaging model in unstructured natural-variation populations, where exhaustive 2^n genotypes are rarely feasible β the model's practical scope remains exhaustively combinatorial mutant panels. What would change the verdict: demonstration on independent multi-gene datasets (e.g., yeast or plant combinatorial CRISPR panels) where averaging-model estimates are unstable or less predictive than additive alternatives.
Author review links: Fumiaki Katagiri
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