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At least 235 records · Page 13Linked to original sources
PubMed2001

A homozygous missense mutation in the tyrosine E kinase domain of the RET proto-oncogene in an infant with total intestinal aganglionosis.

Germline mutations of the RET proto-oncogene (RET), its ligand glial cell-derived neurotrophic factor (GDNF), and neurturin (NTN) gene have been reported in patients with Hirschsprung's disease. A targeted mutation in the tyrosine kinase domain of RET produced total intestinal aganglionosis and renal agenesis in homozygous transgenic mice. Here we describe a homozygous mutation of the human gene for the RET tyrosine kinase domain that was present in a male neonate with total intestinal aganglionosis. Gut wall biopsy specimens from the stomach to the anorectum showed no ganglion cells. No urinary tract abnormalities were detected. Genomic DNAs were isolated from peripheral blood lymphocytes of the infant and his parents. DNA sequences of all the RET/GDNF/NTN coding regions were determined using a direct DyeDeoxy Terminator Cycle method. A homozygous missense mutation (CGG-to-TGG) at RET codon 969 was identified in this patient, which resulted in an amino acid change from arginine to tryptophan. No germline RET/GDNF/NTN mutations were found in his parents. In this case, the homozygous RET mutation seemed to cause a critical alteration of the Ret tyrosine kinase activity, which resulted in total intestinal aganglionosis but not renal agenesis. Discrepancies in phenotypic expression between humans and mice suggest differing threshold values for RET signal transduction in species or organs.

Drosophila Proteins↗
PubMed1993

Molecular characterization of a thyroid tumor-specific transforming sequence formed by the fusion of ret tyrosine kinase and the regulatory subunit RI alpha of cyclic AMP-dependent protein kinase A.

The ret oncogene frequently has been found activated in papillary thyroid carcinomas. A previous characterization of ret activation revealed recombination of its tyrosine kinase domain and sequences derived from an uncharacterized locus (D10S170). The mechanism leading to this recombination was identified as a paracentric inversion of the long arm of chromosome 10, inv(10)(q11.2q21), with the breakpoints occurring where ret and D10S170 were mapped. To further characterize the activation of ret in papillary thyroid carcinomas, we have now isolated and sequenced a second type of ret oncogenic rearrangement not involving the D10S170 locus. The nucleotide sequence indicated that the transforming activity was created by the fusion of the ret tyrosine kinase domain with part of the RI alpha regulatory subunit of protein kinase A (PKA). This is the first example of an oncogenic activity involving a PKA gene. PKA is the main intracellular cyclic AMP receptor, and its RI alpha subunit gene is located on chromosome 17q. RI alpha-ret transcripts encode two isoforms of the chimeric protein (p76 and p81), which display constitutive tyrosine phosphorylation as well as a tyrosine kinase enzymatic activity. Under nonreducing conditions, both isoforms are found in a dimeric configuration because of both homo- and heterodimer formation. Thus, the in vivo activation of ret in human papillary thyroid carcinomas is provided by the fusion of its tyrosine kinase domain with different genes and can be mediated by different mechanisms of gene rearrangement.

3T3 Cells↗
PubMed1995

Mechanism of activation of the ret proto-oncogene by multiple endocrine neoplasia 2A mutations.

Transforming activity of the c-ret proto-oncogene with multiple endocrine neoplasia (MEN) 2A mutations was investigated by transfection of NIH 3T3 cells. Mutant c-ret genes driven by the simian virus 40 or cytomegalovirus promoter induced transformation with high efficiencies. The 170-kDa Ret protein present on the cell surface of transformed cells was highly phosphorylated on tyrosine and formed disulfide-linked homodimers. This result indicated that MEN 2A mutations induced ligand-independent dimerization of the c-Ret protein on the cell surface, leading to activation of its intrinsic tyrosine kinase. In addition to the MEN 2A mutations, we further introduced a mutation (lysine for asparaginic acid at codon 300 [D300K]) in a putative Ca(2+)-binding site of the cadherin-like domain. When c-ret cDNA with both MEN 2A and D300K mutations was transfected into NIH 3T3 cells, transforming activity drastically decreased. Western blot (immunoblot) analysis revealed that very little of the 170-kDa Ret protein with the D300K mutation was expressed in transfectants while expression of the 150-kDa Ret protein retained in the endoplasmic reticulum was not affected. This result also demonstrated that transport of the Ret protein to the plasma membrane is required for its transforming activity.

3T3 Cells↗
PubMed2000

Multiple endocrine neoplasia type 2 and RET: from neoplasia to neurogenesis.

Multiple endocrine neoplasia type 2 (MEN 2) is an inherited cancer syndrome characterised by medullary thyroid carcinoma (MTC), with or without phaeochromocytoma and hyperparathyroidism. MEN 2 is unusual among cancer syndromes as it is caused by activation of a cellular oncogene, RET. Germline mutations in the gene encoding the RET receptor tyrosine kinase are found in the vast majority of MEN 2 patients and somatic RET mutations are found in a subset of sporadic MTC. Further, there are strong associations of RET mutation genotype and disease phenotype in MEN 2 which have led to predictions of tissue specific requirements and sensitivities to RET activity. Our ability to identify genetically, with high accuracy, subjects with MEN 2 has revolutionised our ability to diagnose, predict, and manage this disease. In the past few years, studies of RET and its normal ligand and downstream interactions and the signalling pathways it activates have clarified our understanding of the roles played by RET in normal cell survival, proliferation, and differentiation, as well as in disease. Here, we review the current knowledge of the normal functions of RET and the effects of mutations of this gene in tumorigenesis and in normal development.

Carcinoma, Medullary↗
PubMed2005

RET-familial medullary thyroid carcinoma mutants Y791F and S891A activate a Src/JAK/STAT3 pathway, independent of glial cell line-derived neurotrophic factor.

The RET proto-oncogene encodes a receptor tyrosine kinase whose dysfunction plays a crucial role in the development of several neural crest disorders. Distinct activating RET mutations cause multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN2B), and familial medullary thyroid carcinoma (FMTC). Despite clear correlations between the mutations found in these cancer syndromes and their phenotypes, the molecular mechanisms connecting the mutated receptor to the different disease phenotypes are far from completely understood. Luciferase reporter assays in combination with immunoprecipitations, and Western and immunohistochemistry analyses were done in order to characterize the signaling properties of two FMTC-associated RET mutations, Y791F and S891A, respectively, both affecting the tyrosine kinase domain of the receptor. We show that these RET-FMTC mutants are monomeric receptors which are autophosphorylated and activated independently of glial cell line-derived neurotrophic factor. Moreover, we show that the dysfunctional signaling properties of these mutants, when compared with wild-type RET, involve constitutive activation of signal transducers and activators of transcription 3 (STAT3). Furthermore, we show that STAT3 activation is mediated by a signaling pathway involving Src, JAK1, and JAK2, differing from STAT3 activation promoted by RET(C634R) which was previously found to be independent of Src and JAKs. Three-dimensional modeling of the RET catalytic domain suggested that the structural changes promoted by the respective amino acids substitutions lead to a more accessible substrate and ATP-binding monomeric conformation. Finally, immunohistochemical analysis of FMTC tumor samples support the in vitro data, because nuclear localized, Y705-phosphorylated STAT3, as well as a high degree of RET expression at the plasma membrane was observed.

Adenosine Triphosphate↗
PubMed2002

5'-End RET splicing: absence of variants in normal tissues and intron retention in pheochromocytomas.

The Ret tyrosine kinase is implicated in neuronal cell survival, kidney development and tumorigenesis. Several 3' and 5' transcript variants have been described resulting from alternative splicing of the RET pre-mRNA. The 3' variants code for three C-terminal isoforms, RET51, RET9 and RET43. The 5' variants RET2/4, RET2/5 and RET2/6 result from skipping exons 3, 3-4 and 3-5, respectively. These variants code for putative Ret proteins differing in their extracellular ligand-binding domains, and their expression is strongly regulated during kidney development. Here we analyzed the presence of these RET 5' variants in normal tissues and in MEN2 and sporadic pheochromocytomas. In all tissues examined, the abundance of these transcripts remained extremely low (less than 1% of all RET transcripts) thus indicating these species as rare variants with little biological meaning. On the other hand, in tumors, the 5' RET splicing pattern differed from that of normal tissues. Indeed, we identified a RET-derived transcript that results from the aberrant retention of intron 2. This transcript is enriched in tumor samples of both familial and sporadic origin, and indicates RET as a target for RNA splicing deregulation in tumor cells.

5' Untranslated Regions↗
PubMed2006

Molecular implications of RET mutations for pheochromocytoma risk in multiple endocrine neoplasia 2.

Multiple endocrine neoplasia Type 2 (MEN 2) is an inherited cancer syndrome characterized by medullary thyroid carcinoma (MTC). The disease has three subtypes, which are distinguished by the presence of additional phenotypes. In particular, pheochromocytoma occurs in approximately 50% of patients with the MEN 2A or MEN 2B subtypes, but is not found in patients with the milder disease subtype, familial MTC (FMTC). All subtypes of MEN 2 are caused by activating mutations of the RET (REarranged in Transfection) proto-oncogene. RET encodes a transmembrane receptor tyrosine kinase, required for development of neuroendocrine cell types and the kidneys. All MEN 2 subtypes are associated with single amino acid substitution mutations that are found in either the extracellular domain or in the kinase domain of RET. There are strong genotype-phenotype correlations in MEN 2 between patient phenotype and the specific residue that is mutated. MEN 2A is primarily associated with substitutions at five extracellular cysteine residues, while 95% of MEN 2B is associated with a single methionine to threonine mutation in the kinase domain (M918T). In FMTC, RET mutations are more broadly distributed, with both extracellular cysteines and intracellular sites implicated. In all cases, MEN 2-RET mutations result in constitutive activation of the receptor, although the mechanism and relative functional effects of the mutations vary. Recent advances in functional characterization and development of molecular models of RET and of various MEN 2-RET mutants are helping us understand tissue-specific differences in oncogenic potential conferred by the different RET mutations. Here, we discuss and compare several well-characterized mutations of the extracellular and kinase domains, which have quite varied functional implications.

Adrenal Gland Neoplasms↗
PubMed1997

Only the substitution of methionine 918 with a threonine and not with other residues activates RET transforming potential.

Specific point-mutations of the RET receptor tyrosine kinase protooncogene are responsible for the inheritance of multiple endocrine neoplasia type 2A (MEN2A) and 2B (MEN2B), and familial medullary thyroid carcinoma (FMTC). MEN2B is caused by the substitution of methionine 918 by a threonine in the tyrosine kinase (TK) domain of RET. This mutation converts RET into a dominant transforming oncogene. We have substituted Met918 with four different residues and found that RET acquired transforming activity only when Met918 was substituted with a threonine. However, also when serine and valine, but not leucine or phenylalanine, were inserted in position 918, the RET TK function was activated and induced, especially in the case of the RET(918Ser), immmediate-early response genes. We conclude that the preservation of Met918 is critical for the control of RET kinase. However, only when a threonine residue is present in position 918, does RET efficiently couple with a transforming pathway.

3T3 Cells↗
PubMed2004

A new germline RET mutation apparently devoid of transforming activity serendipitously discovered in a patient with atrophic autoimmune thyroiditis and primary ovarian failure.

Gain-of-function RET mutations are responsible for multiple endocrine neoplasia syndromes (MEN) 2A and 2B and familial medullary thyroid carcinoma (FMTC), whereas loss-of-function mutations are found in Hirschsprung disease. We report a new RET point mutation [R694Q (CGG-->CAG)], serendipitously found in a 23-yr-old woman with hypothyroidism due to atrophic Hashimoto's thyroiditis and primary ovarian failure, without altered calcitonin secretion. Familial history and clinical and biochemical evaluation of first-degree relatives were negative for FMTC, MEN 2A and 2B, and Hirschsprung disease. Genetic analysis showed that the mutation was inherited from the mother, who was submitted 2 yr before to thyroidectomy for goitrous Hashimoto's thyroiditis. Histological revision and immunohistochemical studies documented normal C cell number and morphology. We cloned the mutation in an expression vector encoding a full-length RET protein. The construct was transiently expressed in 293T cells in parallel with a wild-type RET and a C634R MEN 2A-associated RET mutant. Proteins were harvested from transfected cells, and tyrosine phosphorylation levels were assayed. The mutation did not exert significant potentiating effects on RET kinase. A focus assay was also performed on NIH3T3 fibroblasts; the mutant did not exert significant transforming activity. In conclusion, a new RET mutation was found in two subjects without any evidence of MEN and FMTC. In keeping with clinical data, transfection studies confirmed lack of activating activity. This serendipitous discovery, apparently devoid of oncogenic potential, underscores the problems that may be encountered in genomic studies on RET.

Adult↗
PubMed2002

Glial-derived neurotropic factor and RET gene expression in normal human anterior pituitary cell types and in pituitary tumors.

Glial-derived neurotropic factor (GDNF) signaling is mediated through a 2-component system consisting of the so-called GDNF receptor-alpha (GFRalpha1), which binds to GDNF. This complex activates the tyrosine kinase receptor RET. In this paper we demonstrate GDNF, GFRalpha1, and RET mRNA and protein expression in the human anterior pituitary gland. Double immunohistochemistry of anterior pituitary sections showed GDNF immunoreactivity in more than 95% of somatotrophs and to a lesser extent in corticotrophs (20%); it was almost absent in the remaining cell types. Also, although more than 95% of somatotrophs were stained for RET, no positive immunostaining could be detected in other cell types. Furthermore, we have looked for GDNF and RET in human pituitary adenomas of various hormonal phenotypes. Strong positive immunostaining was found for c-RET in all of the GH-secreting adenomas screened as well as in 50% of ACTH-producing adenomas. Positive immunostaining for GDNF was found in all of the GH-secreting adenomas and in 10% of the corticotropinomas. Lastly, we found strong positive immunostaining for GFRalpha1 in 90% of the somatotropinomas and 50% of the corticotropinomas as well as in 1 of 8 prolactinomas and 1 of 13 nonfunctioning adenomas. All of the remaining pituitary tumors screened were negative for RET, GDNF, and GFRalpha1. This study indicates that GDNF may well be acting in the regulation of somatotroph cell growth and/or cell function in the normal human anterior pituitary gland. The expression of RET in all of the somatotropinomas and in 50% of the ACTH-producing tumors implies that GDNF and RET could be involved in the pathogenesis of pituitary tumors.

Adenoma↗
PubMed2004

Biological effects of the dual phenotypic Janus mutation of ret cosegregating with both multiple endocrine neoplasia type 2 and Hirschsprung's disease.

Gain-of-function mutations of ret receptor tyrosine kinase, the signaling receptor for glial cell line-derived neurotrophic factor, cause sporadic thyroid and adrenal malignancies as well as endocrine cancer syndromes, such as multiple endocrine neoplasia types 2A and 2B (MEN 2A and MEN 2B) and familial medullary thyroid carcinoma. Loss-of-function mutations of ret cause Hirschsprung's disease (HSCR) or colonic aganglionosis. In 20-30% of families with a mutation at residues 609, 611, 618, or 620 of RET, MEN 2A and familial medullary thyroid carcinoma cosegregate with HSCR. These mutations constitutively activate RET due to aberrant disulfide homodimerization and diminish the level of RET at the plasma membrane. It is not known how these mutations simultaneously lead to both gain- and loss-of-function RET-associated diseases. We provide an explanation for the dual phenotypic Janus mutation at Cys620 of RET. In Madin-Darby canine kidney (MDCK) cells, the Janus mutation impairs the glial cell line-derived neurotrophic factor-induced effects of RET on cell migration, differentiation, and survival but simultaneously promotes rapid cell proliferation.

Animals↗
PubMed1995

Oncogenic activation of the ret protooncogene in thyroid cancer.

Recent studies have established that the ret protooncogene is involved in the development of thyroid tumors, including medullary and papillary thyroid carcinomas. Germ line mutations of the ret protooncogene were identified in multiple endocrine neoplasia (MEN) types 2A and 2B that share the clinical feature of medullary thyroid carcinoma and pheochromocytoma. MEN 2A mutations involved cysteine residues in the extracellular domain and induced disulfide-linked homodimerization of the Ret protein on the cell surface, leading to activation of its intrinsic tyrosine kinase. On the other hand, a single point mutation in the tyrosine kinase domain was found in MEN 2B, as well as in 30 to 40% of sporadic medullary carcinoma. This mutation also resulted in activation of Ret tyrosine kinase without the formation of its covalent homodimerization. Differences in the mechanisms of ret activation might account for the different phenotypes observed in MEN 2A and MEN 2B. In addition, somatic rearrangement of the ret protooncogene was frequently detected in papillary thyroid carcinoma, particularly from adult Europeans. A recent report demonstrated that the same rearrangement was observed in approximately 60% of papillary carcinomas of children from areas contaminated by the Chernobyl accident, suggesting that ret rearrangement was induced as a direct consequence of radiation exposure. In this review, I focus on the ret mutations detected in thyroid cancer and discuss the mechanisms of its oncogenic activation.

Carcinoma, Papillary↗
PubMed2005

[Immunohistochemical study of RET protein in Hirschsprung's disease and allied Hirschsprung's disorder].

OBJECTIVE: Hirschsprung's Disease (HD) and allied Hirschsprung's disorder (HAD) have very similar clinical manifestations, but there are many different theories about the two diseases. The present study was designed to understand the expression of Ret protein in HD and HAD, and to explore the role of Ret protein in the pathogenesis of HD and HAD. METHODS: Colon specimens from patients with confirmed HD and HAD, including 15 cases of HD (male 12, female 3) and 11 cases of HAD (male 8, female 3) were collected for this study. At the same time normal colon specimens from 10 individuals with other diseases were used as control. The expression of Ret protein in the intestinal tissue was detected by using immunohistochemical SABC technique with mouse anti-Ret monoclonal antibody. RESULTS: In the colon specimens from normal controls and the dilated segments of colon from HD and HAD patients, moderate to large number of Ret-positive cells were observed among the ganglion cells of myenteric plexuses and submucosal plexuses (P > 0.05). On the contrary, Ret-positive cells were not seen in the stenotic segment of colon from HD patients. But there was positive staining in the stenotic segment of the colon from HAD. Moreover, giant ganglion cells showing strongly positive staining could be seen. There were also displastic cells, small cells, and cells with irregular shape. Statistical analysis showed significant differences in Ret cells positivity between the stenotic segment of colon of HD and the normal control (P < 0.001) as well as between HD and HAD (P < 0.001). CONCLUSION: Ret protein may play an important role in the pathogenesis of HD and could not have definite relationship with HAD.

Case-Control Studies↗
PubMed1988

Cloning and expression of the ret proto-oncogene encoding a tyrosine kinase with two potential transmembrane domains.

The nucleotide sequence of the ret proto-oncogene has been determined from cDNA clones isolated from a cDNA library of a THP-1 human monocytic leukemia cell line. Analysis of this sequence indicates that it encodes a protein which is structurally related to transmembrane receptors with a cytoplasmic tyrosine kinase domain. Unlike most growth factor receptors, it contains two hydrophobic regions which are potential transmembrane domains. Comparison of the sequence of the ret proto-oncogene with that of the ret transforming gene revealed that, in addition to the amino-terminal truncation, the last 51 carboxy-terminal amino acids of the ret proto-oncogene were replaced with 9 unrelated amino acids of the ret transforming gene. The focus forming activity of the ret cDNA, containing both amino-terminal and caboxy-terminal truncations, was approximately 13-fold higher than that of cDNA containing only the amino-terminal truncation. This suggests a possible role for the carboxy-terminal sequence in activation of transforming potential of the ret proto-oncogene. When transcription of the ret proto-oncogene was examined in a variety of mouse tissues, we detected its transcription in normal mouse spinal cord and lymphadenopathy of C3H/HeJ-gld/gld and MRL/Mp-lpr/lpr mice.

Amino Acid Sequence↗
PubMed1994

The oncogenic versions of the Ret and Trk tyrosine kinases bind Shc and Grb2 adaptor proteins.

Proto-TRK and proto-RET genes encode receptor type tyrosine kinases. Oncogenic rearrangements of both proto-oncogenes have been detected with a significant frequency in human papillary thyroid carcinomas. Chimeric Ret and Trk oncoproteins, encoded by different rearrangements of proto-TRK and proto-RET genes, display a constitutive phosphorylation on tyrosine. Moreover, it has been shown that phosphorylated tyrosine receptors, activated by their ligands, form multiprotein complexes responsible for transducing mitogenic or differentiation signals. We have therefore begun to analyse in this study the signal transduction pathways triggered by different Ret and Trk oncoproteins. We have shown that the SH2 domain of the adaptor protein Shc coimmunoprecipitates with all the Ret and Trk oncoproteins as well as with NGF-activated proto-Trk receptor. Tyrosine phosphorylation of Trk proteins both normal and oncogenic is necessary for their binding to Shc. In addition, in cells containing either Ret or Trk oncoproteins, Shc proteins are constitutively phosphorylated on tyrosine and bound to Grb2. Only in in vitro experiments were Ret and Trk oncoproteins shown to bind the SH2 region of Grb2. Finally, when proto-Trk product is stimulated by NGF, Shc phosphorylation and association with Grb2 are induced. In conclusion, we have shown that Ret and Trk oncoproteins can form multiprotein complexes, however, the functional meaning of the described interactions has to be elucidated.

3T3 Cells↗
PubMed1995

Expression of the RET oncogene induces differentiation of SK-N-BE neuroblastoma cells.

Expression of the RET proto-oncogene, a cell surface receptor for an as yet unknown ligand, is associated with tumors, tissues, and cell lines of neural crest origin. Accumulating evidence suggests that RET activity is involved in the process of neuronal differentiation. Moreover, induction of phenotypic differentiation of neuroblastoma cell lines is associated with the rapid accumulation of RET transcripts. To verify the role of RET in neuronal differentiation, we introduced into the human neuroblastoma cell line SK-N-BE four versions of the RET oncogene, activated by different mechanisms: RET/PTC1 and RET/PTC3, which are activated by rearrangement with heterologous genes; and two activated RET mutants, which carry the single amino acid substitution found associated to the inheritance of the multiple endocrine neoplasia type 2A (retMEN2A allele) and type2B (retMEN2B allele), respectively. We demonstrate that, after transfection with the RET oncogenes, SK-N-BE cells display a reduced growth rate and acquire a neurite-bearing phenotype accompanied by enhanced expression of the axonal growth-associated protein, GAP-43, and the high molecular weight neurofilament, NF200. These results indicate that, when activated, RET is able to cause growth inhibition and to promote neuronal differentiation of neuroblastoma cells.

Blotting, Northern↗
PubMed2005

Mutation of retS, encoding a putative hybrid two-component regulatory protein in Pseudomonas aeruginosa, attenuates multiple virulence mechanisms.

Two-component regulatory systems play an important role in bacterial virulence. We report that mutation of a Pseudomonas aeruginosa gene designated retS (previously designated fimK; accession number PA4856) encoding a putative hybrid two-component regulator, attenuates multiple virulence mechanisms. The retS mutant was selected from a Tn5 transposon library of the cytotoxic P. aeruginosa strain PA103 based upon expression of a small-colony phenotype suggestive of reduced surface-associated "twitching" motility, a property dependent upon type IV pili. Subsequent analysis revealed that the mutant expressed pilin, albeit at lower levels than wild-type PA103. In a murine model of corneal infection, retS mutation was associated with delayed disease development and altered pathology. In vitro, retS mutants demonstrated loss of acute cytotoxic activity towards corneal epithelia as determined by trypan blue exclusion and by LDH release assays (P<0.0001). This coincided with loss of ExsA-regulated type III secretion. Mutation of retS also impaired ExsA-independent pathogenic mechanisms. When compared to the exsA mutant of PA103, retS mutants exhibited reduced epithelial adherence and invasion and reduced intracellular survival within the cells after invasion. Time-lapse video microscopy revealed that retS mutants, compared to exsA mutants, had a reduced capacity to access, and move along, the basal cell surfaces of corneal epithelial cell monolayers. Taken together, these data suggest that the protein encoded by retS regulates various properties of P. aeruginosa including both ExsA-dependent and ExsA-independent virulence mechanisms.

Animals↗
PubMed1997

RET proto-oncogene is important for the development of respiratory CO2 sensitivity.

Brain stem muscarinic cholinergic pathways are important in respiratory carbon dioxide (CO2) chemosensitivity. Defects in the muscarinic system have been reported in children with congenital/developmental disorders of respiratory control such as sudden infant death syndrome (SIDS) and congenital central hypoventilation syndrome (CCHS). This early onset of disease suggests a possible genetic basis. The muscarinic system is part of the autonomic nervous system which develops from the neural crest. Ret proto-oncogene is important for this development. Thus, a potential role for ret in the development of respiratory CO2 chemosensitivity was considered. Using plethysmography, we assessed the ventilatory response to inhaled CO2 in the unanesthetized offsprings of ret +/- mice. Fractional increases in minute ventilation during hypercapnia relative to isocapnia were 5.1 +/- 3.2, 3.0 +/- 1.6 and 1.4 +/- 0.8 for the ret +/+, ret +/- and ret +/- mice, respectively. The ret knockout mice have a depressed ventilatory response to inhaled CO2. Therefore, the ret gene is an important factor in the pathway of neuronal development which allow respiratory CO2 chemosensitivity.

Animals↗