B6.129S1(FVB)-Ret^tm2.1Cos/J

Stock number: 016234
Research areas: Cancer Research, Endocrine Deficiency Research

Description

These Ret^MEN2B mice contain a point mutation (M919T) in codon 919 (exon 16) of the Ret gene, and may be useful for studying the role of this mutation in the development of multiple endocrine neoplasia type 2.

Detailed description

These Ret^MEN2B mice contain a point mutation (M919T) in codon 919 (exon 16) of the Ret proto-oncogene (Ret) gene. This mutation corresponds to mutations in human codon 918 commonly found in humans with multiple endocrine neoplasia type 2 (MEN2). This construct also contains two silent mutations in codons 920 and 921, which abolish a restriction site and allows for detection. Females homozygotes are fertile while male homozygotes are sterile. Homozygotes, while viable, have a reduced life span. Ret encodes a receptor tyrosine kinase which serves as a receptor for glial cell derived neurotrophic factor (GDNF). RET is expressed in excretory, central, and peripheral nervous systems, neural crest, enteric nervous system (ENS), and neuroendocrine cells such as C cells of the thyroid and chromaffin cells of the adrenal gland. This methionine mutation in the catalytic core accounts for 95% of human MEN2B cases. Heterozygous mice display C cell and chromaffin hyperplasia and pheochromocytoma. Homozygotes exhibit more severe thyroid and adrenal disease as well as ganglioneuroma of the adrenal medulla, and enlargement of the sympathetic ganglia. These mice do not develop medullary thyroid carcinoma or ganglioneuroma of the gastrointestinal tract or mucosa as humans afflicted with MEN2B do. These mice may be useful for studying the role of RET M919T mutation in the development of MEN2B.

Development

A targeting vector was designed to insert a loxP-flanked neomycin resistance (neo) cassette upstream of exon 16 of the Ret proto-oncogene (Ret) gene. Ret exon 16 also contains a tyrosine to cytosine point mutation in codon 919, resulting in the M919T mutation, and two silent mutations in codons 920 and 921. The construct was electroporated into 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺-derived W9.5 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts and resulting chimeric mice were bred to Tg(ACTB-cre)2Mrt mice on an FVB background to delete the neo cassette. Progeny were crossed to remove the Cre-expressing transgene, and the resulting Ret^MEN2B mice were backcrossed to C57BL/6J mice for at least 20 generations. Upon arrival, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the colony.

Allele

Symbol: Ret^tm2.1Cos
Name: targeted mutation 2.1, Frank Costantini
MGI accession ID: MGI:2136896
Generation method: Targeted
Attributes: Humanized sequence
Marker symbol: Ret
Marker name: ret proto-oncogene
Chromosome: 6
Strain of origin: 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺
Molecular note: A T to C transition in codon 919, the equivalent codon to human 918, resulted in a protein which encoded threonine instead of methionine at this position. This mutation corresponds to mutations in human codon 918 commonly found in humans with multiple endocrine neoplasia type 2 (MEN2). Silent mutations in codons 920 and 921 abolished a MunI endonuclease site. An adjacent loxP flanked neomycin cassette was removed by crossing mice carrying Ret^tm2Cos to mice expressing Cre under the control of a Beta-actin promoter.