Table 1_From chromatin to proteostasis: multilevel gene regulation in Mendelian diseases.docx

The diagnostic challenge is not to catalogue these layers, but to determine which regulatory mechanism is plausible for a given variant, phenotype, tissue and developmental context. This targeted narrative review synthesises representative Mendelian mechanisms across five linked levels: chromatin, transcription, RNA processing and stability, translation, and post-translational proteostasis.

Three cross-cutting principles recur. First, distinct molecular lesions may converge on the same functional bottleneck: altered dosage, timing, localisation or disrupted protein homeostasis. Second, regulatory effects are often cell-type-, isoform-, developmental-stage- and state-specific, so assay and tissue selection are integral to interpretation.