| First Author | Kurosawa T | Year | 1993 |
| Journal | Mouse Genome | Volume | 91 |
| Issue | 4 | Pages | 876-78 |
| Mgi Jnum | J:16284 | Mgi Id | MGI:64368 |
| Citation | Kurosawa T, et al. (1993) Nephrosis (nep): a new mouse mutation which causes albuminuria and other symptoms of nephrosis. Mouse Genome 91(4):876-78 |
| abstractText | Full text of Mouse Genome contribution: NEPHROSIS (nep) : A NEW MOUSE MUTATION WHICH CAUSES ALBUMINURIA AND OTHER SYMPTOMS OF NEPHROSIS. Tsutomu Kurosawa, Munehiro Okamoto, Kanae Yamada, and Bing Fei Yue, The Institute of Exprimental Animal Sciences, Osaka University Medical School, 2-2 Yamadaoka, Suita-shi, Osaka, Japan. Abstract We have characterized a new recessive mutation in the mouse which predisposes the development of albuminuria and other symptoms of nephrosis. In the previous study, the appearance of this renal disease was presumed to be controlled by autosomal recessive genes. We have carried out progeny testing by urinalysis using SDS-PAGE. We have determined that the mode of inheritance of naturally occurring albuminuria in the nephrotic mice is a single autosomal recessive mutation. Introduction This mutation, called nephrosis (nep), arose from an outbred ICR mouse colony at the National Institute of Health (Japan) in 1986(1). Generally the affected mice show a nephrotic syndrome which is characterized with proteinuria, hypoalbuminemia, hyperlipidemia and edema. Extensive histopathological studies of progressively staged mice indicated glomerular lesions consisting of a marked thickening of the glomerular basement membrane, multilaminar splitting of the lamina densa of the basement membrane and fusion of the epithelial foot process 2-4. Although albuminuria is evident as early as two days of life, microscopic renal lesions are not prominent in young affected mice (unpublished data). Because unaffected parents could produce affected offspring, the involvement of recessive gene(s) in the onset of the disease has already been suggested1. They however also noted that the mode of inheritance seemed rather complex as there were sex-related differences in the incidence of the disease in backcross Fl mice (DBA/2-ICGN Fl x ICGN)4. To elucidate the mode of inheritance of this renal disease, we focused on the occurrence of albuminuria which may be the primary cause of this disease rather than the various renal lesions observed in the terminal stage4. We analyzed urine of the progeny mice obtained from the mating between the affected males (presumptive homozygote) and, unaffected females and males which were presumably heterozygous with sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)5. Materials and Methods Animals: The animals used were kept in an animal room with controlled temperature (23 +/- 1 C), humidity (55 +/- 15 %) and lighting (12 hours light and 12 hours dark). They were fed with normal laboratory chow (MF, Oriental Yeast Co., Ltd) and tap water ad libitum. Urinalysis: The urine was collected with glass tubes. Urine samples were analyzed with SDS-PAGE as described by Laemmli5 to detect the albumin fraction. The electrophoresis system used was a mini- slab with a 12 % gel. The gel was stained with coomassie brilliant blue R-250. The markers used for SDS-PAGE were 97.4, 66.1, 45, 31, 21.5, and 14.4 kD. The protein fraction that appeared at 66.1 kD was ascertained to be an albumin fraction and mice with urine that showed the 66.1 kD fraction were designated as affected. Progeny test: The affected males (presumptive homozygotes) were mated with the presumptive heterozygous females. The presumptive heterozygous males were also mated with the presumptive heterozygous females. Because the affected females did not consistently care for their litters, the progeny test was not carried out in the affected females. The data obtained were analysed with Chi square test. Results A band of 66.1 kD was clearly identified in SDS-PAGE in affected mice (Fig. 1). Some other bands were also recognized in affected mice. Except for the band at about 23 kD which was thought to be a major urinary protein, there were not any bands in unaffected and ICR mice in SDS-PAGE. The affected males (homozygotes) were mated with the unaffected but possible carrier females (presumptive heterozygotes) and 23 and 26 unaffected females and males respectively were obtained. In these mating, the numbers of affected progeny were 27 females and 28 males. The unaffected males but carriers (presumptive heterozygotes) were mated with the unaffected carrier females (presumptive heterozygotes) and 13 affected females and 11 affected males and 44 unaffected females and 45 unaffected males were obtained in 19 litters (Table 1). Discussion The present results of the progeny test demonstrate that the mode of inheritance of albuminuria in the nephrotic mice is single autosomal recessive. Although the other symptoms of nephrosis and the renal lesions may be dominated by more complex genes 3, 4, at least the development of albuminuria which is one of the major symptoms and the primary cause of nephrosis is determined to be dominated by a single autosomal recessive gene. We would like to propose that this mutant gene be named nephrosis (nep). There are a few mouse strains which show renal lesions such as ddY mouse (IgA nephropathy)6, NZB x NZW 7 and MRL/lpr (lupus nephritis)8 and NOD mouse (diabetic nephropathy)9. In the nephrotic mice studied, albuminuria can be detcctcd as young as two days before other light microscopic renal lesions are not recognized yet. The cause of nephrosis in the mice studied might be different from those reported previously. The mice may be useful for examining the unknown cause of nephrosis, particularly the onset of albuminuria in minimal change nephrosis. Because a single gene has been found which predisposes the mice to albuminuria, the nephrotic mice studied can be an excellent model for human nephrotic disease. Further study to determine the gene linkage and gene mapping are being undertaken. The inbreeding of the nephrotic mice is also in progress. And the genetic analysis of other renal lesions may be necessary in future. References 1. Ogura, A., et al. Experimental Animals. 38, 349-352 (1989). 2. Ogura, A., et al. Virchows Archiv A Pathol. Anat. 417, 223-228 (1990). 3. Ogura, A., et al. Laboratory Animals 23, 169-174 (1989). 4. Ogura, A., et al. Proc. of Jap. Soc. of Anim. Bioch. 30, 15-22 (1993). 5. Laemmli, U.K. Nature 227, 680-685 (1970). 6. Imai, H., et al. Kidney International 27, 756-761 (1985). 7. Mellors, R.C. Journal of Pathology 103, 97-105 (1971). 8. Nose, M., et al. Am. J. of Pathol. 135, 271-280 (1989). 9. Watanabe, S. Jap. J. of Nephro1. 31, 1011-1019 (1989). Figure 1 Table 1 Crosses: Female: Carrier (+/nep); Male: Carrier (+/nep); No. of crosses (Litters); 4 (19); No. of progeny: 113; Unaffected: Females: 44, Males: 45, Total: 89; Affected: Females: 13, Males: 11, Total: 24; Expected segregation ratios*: 3 : 1; X2 (P) 0.853 (P=0.3558). Crosses: Female: Carrier (+/nep); Male: Affected (nep/nep); No. of crosses (Litters): 11 (12); No. of progeny: 104; Unaffected: Females: 23, Males: 26, Total: 49; Affected: Females: 27, Males: 28, Total: 55; Expected segregation ratios*: 1 : 1; X2 (P): 0.033 (P=0.8563). *On the assumption that a single autosomal recessive gene is responsible for the trait. |
