Your Query returns 4 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
Rtn1-aNM_15345710090Nsp    Rtn1-b    Rtn1-c    MGC40985    0710005K15Rik    Rtn1   
Rtn1-aBC03045510090Nsp    Rtn1-c    MGC40985    Rtn1-b    Rtn1   
Rtn1-aBC05857910090Nsp    Rtn1-c    MGC40985    Rtn1-b    Rtn1   
Rtn1-aBC05392610090Nsp    Rtn1-c    MGC40985    Rtn1-b    Rtn1   

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

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Text2Knowledge ... Yong Huang 2002