The ZEB2 gene is expressed (i.e. makes a protein product) in a variety of tissues, but in particular, it plays an essential role in the correct developement of the nervous system.
MWS is caused by a change (known as a variants or mutation) in one of the two copies of ZEB2 a person has, while the other copy is normal. Different types of changes in the gene can occur, but all the variants that cause MWS are expected to either stop the expression or alter the function of that copy of the gene. These are called pathogenic or likely pathogenic variants. Those changes include single variants (changes in the spelling of the gene code), deletions (missing part or all of the gene) and sometimes rearrangements (swapping around of sections of the gene code or chromosomes).
When there is not enough normal ZEB2 protein, this can effect many different developmental pathways, which is why the features of MWS can involve facial appearance and other body organs, as well as brain development.
ZEB2