To this end, we crossed the RIPDTR allele with the Clec4f-Cre-tdTomato allele, a knock-in allele in which the C-type lectin domain family 4 member f, Clec4f, promoter drives expression of Cre-recombinase and TdTomato only in KCs (36). The gene discussed is CLEC4F; the disease is dry eye syndrome.