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|Coordinate||29,069,090 bp (GRCm38)|
|Base Change||C ⇒ A (forward strand)|
|Chromosomal Location||29,060,220-29,073,877 bp (+)|
|MGI Phenotype||Strain: 1856424
FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] This gene encodes a protein that is secreted by white adipocytes, and which plays a major role in the regulation of body weight. This protein, which acts through the leptin receptor, functions as part of a signaling pathway that can inhibit food intake and/or regulate energy expenditure to maintain constancy of the adipose mass. This protein also has several endocrine functions, and is involved in the regulation of immune and inflammatory responses, hematopoiesis, angiogenesis and wound healing. Mutations in this gene and/or its regulatory regions cause severe obesity, and morbid obesity with hypogonadism. This gene has also been linked to type 2 diabetes mellitus development. [provided by RefSeq, Jul 2008]
PHENOTYPE: Homozygotes are obese, hyperphagic, have low activity, high metabolic efficiency, impaired thermogenesis, infertility and short lifespan in addition to varying other abnormalities. Strain background affects severity and course of diabetes. Heterozygotes survive fasting longer than control mice. [provided by MGI curators]
|Amino Acid Change||Histidine changed to Asparagine|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000067046] [ENSMUSP00000130087]|
AA Change: H47N
|Predicted Effect||probably benign
PolyPhen 2 Score 0.272 (Sensitivity: 0.91; Specificity: 0.88)
AA Change: H47N
|Predicted Effect||possibly damaging
PolyPhen 2 Score 0.952 (Sensitivity: 0.79; Specificity: 0.95)
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Recessive|
|Last Updated||2016-05-13 3:09 PM by Anne Murray|
|Record Created||2016-02-09 5:15 PM|
The potbelly2 phenotype was identified among G3 mice of the pedigree R1585, some of which exhibited elevated body weights compared to wild-type controls (Figure 1).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 82 mutations. The body weight phenotype was linked to a mutation in Lep: a C to A transversion at base pair 29,069,090 (v38) on chromosome 6, or base pair 10,628 in the GenBank genomic region NC_000072 encoding Lep. Linkage was found with a recessive model of inheritance (P = 5.69 x 10-4), wherein one affected mouse was homozygous for the variant allele, and 38 unaffected mice were either heterozygous (n = 21) or homozygous (n = 17) for the reference allele (Figure 2).
The mutation corresponds to residue 198 in the mRNA sequence NM_008493 in exon 2 of 3 total exons.
The mutated nucleotide is indicated in red. The mutation results in a histidine (H) to asparagine (N) substitution at position 47 (H47N) in the leptin protein, and is strongly predicted by PolyPhen-2 to be benign (score = 0.272).
The Lep (alternatively, ob) gene encodes leptin, a highly conserved adipocyte-secreted hormone and member of the class I helical cytokine family [Figure 3; (1-3)]. Leptin regulates several physiological processes including appetite, energy homeostasis, body weight, neuroendocrine systems [i.e., the growth hormone axis, thyroid axis, hypothalamic-pituitary-gonadal axis, and adrenal axis (4-7)], immune functions (i.e., thymic homeostasis, secretion of IL-1 and TNF-α, and promotion of Th1-cell differentiation [reviewed in (8)]), and glycaemia [reviewed in (9)].
The 167 amino acid leptin has a 21 amino acid N-terminal signal sequence that is cleaved during leptin maturation (10). Vertebrate leptins have two conserved cysteine residues (Cys117 and Cys167 in mouse leptin) that form an intramolecular disulfide bond between the C-terminus and the beginning of the CD loop (11;12). Three conserved leptin receptor (LepR; see the records for Business class, Cherub, and Well-upholstered) binding sites on leptin have been identified: site I is on the face of helix D and is proposed to bind the cytokine receptor homology 1 (CRH1) or CRH2 domain of the LepR, site II is composed of residues on the surface of helices A and C and binds the CRH2 domain of LepR, and site III is at the N-terminus of helix D at the interface of the N-terminus of helix D and the AB loop and binds the immunoglobulin-like domain of LepR (1;13). Binding site II is proposed to be the main high affinity binding site for receptor-ligand interaction (14;15), while site III is proposed to function in forming the active multimeric complex and activating the receptor (16). Mutagenesis of mouse and human leptins in the proximity of binding site III have identified Tyr-140, Ser-141, and Thr-142 as essential for activation, but not binding, of leptin to LepR (16). In addition to the three binding sites in leptin, the highly conserved GLDFIP sequence at aa 38-43 in human leptin is required for LepR activation (1;17;18).
The leptin tertiary structure resembles that of other class I cytokines in that it has a four-helix bundle (helices A-D) with an up-up-down-down topology (19;20). A nuclear magnetic resonance (NMR) study determined that in mouse leptin, Helix A is amino acids 3-24, Helix B is aa 51-67, Helix C is aa 72-94, and Helix D is aa 122-141 (19). Parallel to the helical bundle is a hydrophobic cylindrical core formed from conserved residues of the four alpha helices (11). Leptin differs structurally from other class I cytokines in that it has a small helical segment (i.e., helix E) within the loop between helices C and D [aa 95-121 (11)].
The potbelly2 mutation results in substitution of histidine 47 for an asparagine. Residue 47 is between helices A and B.
For more information about Lep, please see the record for Potbelly.
Leptin, a systemic hormone, regulates multiple functions of the body including energy utilization and storage, various endocrine axes, bone metabolism, thermoregulation, angiogenesis, immunity and inflammation [reviewed in (21)]. In humans, mutations in LEP are linked to morbid obesity, with or without hypogonadism [OMIM: +164160; (22-24)]. The Lepob (ob) mouse strain (MGI:1856424) is morbidly obese and is characterized by hyperinsulinemia, hyperglucocorticoidemia, hypothalamic hypothyroidism, defects in cell-mediated and humoral immunity, impaired thermogenesis, hyperglycemia, insulin resistance, altered central nervous system activity, reduced metabolic rate of brown adipose tissue, infertility, and lethargy (25;26). The obesity phenotype of the potbelly2 mice mimics that of other Lep mouse models (27-29). Expression and secretion of leptin in the potbelly2 mice has not been examined, but the phenotype suggests that expression and/or secretion of leptin is reduced in the potbelly2 mice.
potbelly2(F):5'- ATCCTATAGCAGGATGGCAGCAGG -3'
potbelly2(R):5'- TTTCAGCAGGCAGCAGTGACAAG -3'
potbelly2_seq(F):5'- CATATTGGGCTCTTGAAAAGTGTC -3'
potbelly2_seq(R):5'- AGTGACAAGAGCCATGACC -3'
1. Denver, R. J., Bonett, R. M., and Boorse, G. C. (2011) Evolution of Leptin Structure and Function. Neuroendocrinology. 94, 21-38.
2. Kochan, Z., Karbowska, J., and Meissner, W. (2006) Leptin is Synthesized in the Liver and Adipose Tissue of the Dunlin (Calidris Alpina). Gen Comp Endocrinol. 148, 336-339.
3. Huising, M. O., Kruiswijk, C. P., and Flik, G. (2006) Phylogeny and Evolution of Class-I Helical Cytokines. J Endocrinol. 189, 1-25.
4. Khan, S. M., Hamnvik, O. P., Brinkoetter, M., and Mantzoros, C. S. (2012) Leptin as a Modulator of Neuroendocrine Function in Humans. Yonsei Med J. 53, 671-679.
5. Roubos, E. W., Dahmen, M., Kozicz, T., and Xu, L. (2012) Leptin and the Hypothalamo-Pituitary-Adrenal Stress Axis. Gen Comp Endocrinol. 177, 28-36.
6. Luque, R. M., Huang, Z. H., Shah, B., Mazzone, T., and Kineman, R. D. (2007) Effects of Leptin Replacement on Hypothalamic-Pituitary Growth Hormone Axis Function and Circulating Ghrelin Levels in ob/ob Mice. Am J Physiol Endocrinol Metab. 292, E891-9.
7. Costa, A., Poma, A., Martignoni, E., Nappi, G., Ur, E., and Grossman, A. (1997) Stimulation of Corticotrophin-Releasing Hormone Release by the Obese (Ob) Gene Product, Leptin, from Hypothalamic Explants. Neuroreport. 8, 1131-1134.
8. Licinio, J., Mantzoros, C., Negrao, A. B., Cizza, G., Wong, M. L., Bongiorno, P. B., Chrousos, G. P., Karp, B., Allen, C., Flier, J. S., and Gold, P. W. (1997) Human Leptin Levels are Pulsatile and Inversely Related to Pituitary-Adrenal Function. Nat Med. 3, 575-579.
9. Ahima, R. S., Prabakaran, D., Mantzoros, C., Qu, D., Lowell, B., Maratos-Flier, E., and Flier, J. S. (1996) Role of Leptin in the Neuroendocrine Response to Fasting. Nature. 382, 250-252.
10. Caro, J. F., Sinha, M. K., Kolaczynski, J. W., Zhang, P. L., and Considine, R. V. (1996) Leptin: The Tale of an Obesity Gene. Diabetes. 45, 1455-1462.
11. Coppari, R., and Bjorbaek, C. (2012) Leptin Revisited: Its Mechanism of Action and Potential for Treating Diabetes. Nat Rev Drug Discov. 11, 692-708.
12. Peelman, F., Van Beneden, K., Zabeau, L., Iserentant, H., Ulrichts, P., Defeau, D., Verhee, A., Catteeuw, D., Elewaut, D., and Tavernier, J. (2004) Mapping of the Leptin Binding Sites and Design of a Leptin Antagonist. J Biol Chem. 279, 41038-41046.
13. Sandowski, Y., Raver, N., Gussakovsky, E. E., Shochat, S., Dym, O., Livnah, O., Rubinstein, M., Krishna, R., and Gertler, A. (2002) Subcloning, Expression, Purification, and Characterization of Recombinant Human Leptin-Binding Domain. J Biol Chem. 277, 46304-46309.
14. Fong, T. M., Huang, R. R., Tota, M. R., Mao, C., Smith, T., Varnerin, J., Karpitskiy, V. V., Krause, J. E., and Van Der Ploeg, L. H. (1998) Localization of Leptin Binding Domain in the Leptin Receptor. Mol Pharmacol. 53, 234-240.
15. Niv-Spector, L., Gonen-Berger, D., Gourdou, I., Biener, E., Gussakovsky, E. E., Benomar, Y., Ramanujan, K. V., Taouis, M., Herman, B., Callebaut, I., Djiane, J., and Gertler, A. (2005) Identification of the Hydrophobic Strand in the A-B Loop of Leptin as Major Binding Site III: Implications for Large-Scale Preparation of Potent Recombinant Human and Ovine Leptin Antagonists. Biochem J. 391, 221-230.
16. Zabeau, L., Defeau, D., Van der Heyden, J., Iserentant, H., Vandekerckhove, J., and Tavernier, J. (2004) Functional Analysis of Leptin Receptor Activation using a Janus kinase/signal Transducer and Activator of Transcription Complementation Assay. Mol Endocrinol. 18, 150-161.
17. Imagawa, K., Numata, Y., Katsuura, G., Sakaguchi, I., Morita, A., Kikuoka, S., Matumoto, Y., Tsuji, T., Tamaki, M., Sasakura, K., Teraoka, H., Hosoda, K., Ogawa, Y., and Nakao, K. (1998) Structure-Function Studies of Human Leptin. J Biol Chem. 273, 35245-35249.
18. Boute, N., Zilberfarb, V., Camoin, L., Bonnafous, S., Le Marchand-Brustel, Y., and Issad, T. (2004) The Formation of an Intrachain Disulfide Bond in the Leptin Protein is Necessary for Efficient Leptin Secretion. Biochimie. 86, 351-356.
19. Zhang, F., Basinski, M. B., Beals, J. M., Briggs, S. L., Churgay, L. M., Clawson, D. K., DiMarchi, R. D., Furman, T. C., Hale, J. E., Hsiung, H. M., Schoner, B. E., Smith, D. P., Zhang, X. Y., Wery, J. P., and Schevitz, R. W. (1997) Crystal Structure of the Obese Protein Leptin-E100. Nature. 387, 206-209.
20. Kline, A. D., Becker, G. W., Churgay, L. M., Landen, B. E., Martin, D. K., Muth, W. L., Rathnachalam, R., Richardson, J. M., Schoner, B., Ulmer, M., and Hale, J. E. (1997) Leptin is a Four-Helix Bundle: Secondary Structure by NMR. FEBS Lett. 407, 239-242.
21. Malendowicz, L. K., Rucinski, M., Belloni, A. S., Ziolkowska, A., and Nussdorfer, G. G. (2007) Leptin and the Regulation of the Hypothalamic-Pituitary-Adrenal Axis. Int Rev Cytol. 263, 63-102.
22. Strobel, A., Issad, T., Camoin, L., Ozata, M., and Strosberg, A. D. (1998) A Leptin Missense Mutation Associated with Hypogonadism and Morbid Obesity. Nat Genet. 18, 213-215.
23. Strosberg, A. D., and Issad, T. (1999) The Involvement of Leptin in Humans Revealed by Mutations in Leptin and Leptin Receptor Genes. Trends Pharmacol Sci. 20, 227-230.
24. Montague, C. T., Farooqi, I. S., Whitehead, J. P., Soos, M. A., Rau, H., Wareham, N. J., Sewter, C. P., Digby, J. E., Mohammed, S. N., Hurst, J. A., Cheetham, C. H., Earley, A. R., Barnett, A. H., Prins, J. B., and O'Rahilly, S. (1997) Congenital Leptin Deficiency is Associated with Severe Early-Onset Obesity in Humans. Nature. 387, 903-908.
25. INGALLS, A. M., DICKIE, M. M., and SNELL, G. D. (1950) Obese, a New Mutation in the House Mouse. J Hered. 41, 317-318.
26. van der Kroon, P. H., Boldewijn, H., and Langeveld-Soeter, N. (1982) Congenital Hypothyroidism in Latent Obese (ob/ob) Mice. Int J Obes. 6, 83-90.
27. Hong, C. J., Tsai, P. J., Cheng, C. Y., Chou, C. K., Jheng, H. F., Chuang, Y. C., Yang, C. N., Lin, Y. T., Hsu, C. W., Cheng, I. H., Chen, S. Y., Tsai, S. J., Liou, Y. J., and Tsai, Y. S. (2010) ENU Mutagenesis Identifies Mice with Morbid Obesity and Severe Hyperinsulinemia Caused by a Novel Mutation in Leptin. PLoS One. 5, e15333.
28. Zhang, Y., Proenca, R., Maffei, M., Barone, M., Leopold, L., and Friedman, J. M. (1994) Positional Cloning of the Mouse Obese Gene and its Human Homologue. Nature. 372, 425-432.
|Science Writers||Anne Murray|
|Authors||Emre Turer and Bruce Beutler|
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