Your Query returns 9 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
Nkx2-5NM_05365110116Nkx2.5    Csx   
nkx2-5NM_1314217955nk2.5    nkx2.5   
Nkx2-5NM_00870010090Csx    Nkx2.5    tinman    Nkx-2.5   
NKX2-5BC0257119606NKX2.5    CSX1    CSX    NKX2E   
NKX2-5NM_0043879606CSX    CSX1    NKX2E    NKX2.5   
Nkx2-5NT_03964910090
Nkx2-5AF08313310090Csx   
Nkx2-5AF2831028355
NKX2-5NT_0231339606

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* OMIM link based on symbol match for human and mouse.

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Text2Knowledge ... Yong Huang 2002