Your Query returns 3 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
Nkx2-6NM_01092010090Tix    Nkx2.6    tinman    Nkx-2.6   
Nkx2-6NT_03960610090
Nkx2-6AF04515010090

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

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Text2Knowledge ... Yong Huang 2002