Your Query returns 8 Accession Numbers:

Query Term	Accession	NCBI Taxonid	Synonyms	Phenotype (OMIM) *
Ctrb1	NM_012536	10116	Ctrb
CTRB1	BC005385	9606	CTRB	118890
CTRB1	AY409497	9606		118890
CTRB1	AY409498	9598
CTRB1	AY409499	10090		118890
CTRB1	NM_001906	9606	CTRB	118890
ctrb1	BC055574	7955	wu:fb61f07 fb61f07
CTRB1	NT_024797	9606		118890

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

Text2Knowledge ... Yong Huang 2002