Purification and properties of arylsulfatase B from high- and low-activity mouse strains

Arylsulfatase B (arylsulfate sulfohydrolase; EC 3.1.6.1) activities in C57BL/6J, SWR/J, and A/J mouse liver approximate a 5:3:1 ratio. Each enzyme was purified to apparent homogeneity, and the properties of the three purified enzymes were compared. The purified enzyme behaved as a monomer with an apparent molecular weight of 50,000. The purified enzyme catalyzed the hydrolysis of p-nitrocatechol sulfate (pNCS), 4-methylumbelliferyl sulfate (4MUS), and chondroitin-4-sulfate (C4S) heptasaccharide. Purified SWR/J arylsulfatase B possessed a higher relative electrophoretic mobility at pH 4.0 than the A/J and C57BL/6J isozymes, and the SWR/J enzyme was more thermostable than either the C57BL/6J or the A/J enzyme. No differences were observed among the three enzymes with respect to their Michaelis constants for 4MUS and pNCS, isoelectric points, responses to inhibitors, pH optima, or electrophoretic mobilities at pH 8.3. The relative in vivo rates of synthesis of C57BL/6J, A/J, and SWR/J arylsulfatase B were comparable.     

Comparative biochemistry of murine arylsulfatase B

Arylsulfatase B was purified 4500-fold from liver and kidney of C57BL/6J mice. Hepatic and renal arysulfatase B are apparently determined by a single structural locus; however, posttranslational modification introduces inter- and intratissue microheterogeneity. Partially purified enzyme from C57BL/6J, A/J, C3H/HeJ, and SWR/J mice has similar catalytic properties. The 4500-fold-purified arylsulfatase B from SWR/J and C3H/HeJ mice was more thermostable than that from C57BL/6J and A/J mice, strongly suggesting that the thermostability difference reflects an alteration of the primary structure of the enzyme. Thermal stability of arylsulfatase B was pH dependent and markedly influenced by buffer anion. Variation of thermostability did not appear accountable for the observed activity variation among these strains; however, this possibility cannot be rigorously excluded by presently available data. Thirty-five murine strains were found to possess the As-1 ^a allele (thermostable enzyme), while As-1 ^b was largely restricted to A and C57 strains.This research was supported by PHS Biomedical Sciences Research Support Grant RR-07030.     

Genetic control of heat sensitivity and activity level of murine arylsulfatase B

BALB/c male mice possess twofold higher kidney p-nitrocatechol-SO4 arylsulfatase B than do A/HeJ male mice; however, their liver arylsulfatase activities are comparable. Twentyfold-purified kidney arylsulfatases B from these two strains have similar Michaelis constants, electrophoretic mobilities, pH optima, and inhibitor profiles; however, the BALB/c enzyme is more heat stable than the A/HeJ enzyme. BALB/c, C3H/HeJ, DBA/2J, and SWR/J mice share an autosomal allele, As-1a, which apparently determines the heat-stable arylsulfatase B, while A/HeJ and C57BL/6J mice possess the As-1b allele, which determines the heat-sensitive enzyme. A second autosomal locus, Asr-1, determines liver arylsulfatase B activity. C57BL/6J mice carry the Asr-1a allele, which results in high liver activities, while C3H/HeJ mice are homozygous for the low-activity allele, Asr-1b. Male mice generally have 30-40% higher kidney activities than females; however, female kidney arylsulfatase activities rise and actually surpass those of males during late pregnancy and lactation.     

Linkage of isozyme loci in the mouse: Phosphoglucomutase-2 (Pgm-2), mitochondrial NADP malate dehydrogenase (Mod-2), and dipeptidase-1 (Dip-1)

The linkages of the isozyme genes Mod-2, Pgm-2, and Dip-1 have been determined in tests with established linkage group markers among inbred strains of mice. Unique alleles for both Mod-2 and Pgm-2 have been observed in the strain of SM/J. Linkage was determined from backcross progeny of the matings C57BL/6J×(SM/J×C57BL/6J)F₁, (SM/J×SWR/J)F₁×SM/J, and (SM/J×SWR/J)F₁×SJL/J. The gene Mod-2 is on linkage group 1. In a three-point cross of the loci Gpi-1, c, and Mod-2, the c locus was determined to be the middle gene. No double crossovers were observed. Our combined data show the following linkages: Gpi-1 to c, 28.3±3.2%; Gpi-1 to Mod-2, 33.3±3.0%; and c to Mod-2, 4.1±2.8%. The proposed gene order for four markers on LG I is Gpi-1-p-c-Mod-2. The gene Pgm-2 was linked to Gpd-1 (27.0±4.2%) on LGVIII. Two backcrosses segregating for Pgm-2 and b, (SM/J×DBA/2J) F₁×DBA/2J and (SM/J×DBA/2J)F₁×C57BR/cdJ, showed 9.1±4.3% recombination. The proposed gene order on LG VIII is b-Pgm-2-Gpd-1. The genes Pgm-1 and Pgm-2 are not linked (53.4±4.4%). Linkage of the isozyme genes Dip-1 and Id-1 on LG XIII was observed in backcross progeny of the crosses (SJL/J×C57BL/6J)F₁×SJL/J and C57BL/6J×(SM/J×C57BL/6J)F₁. The combined recombination was 23.8±2.8%. Two cases are established where genes whose enzyme products share substrate affinities (Pgm-1 and Pgm-2; Mod-1 and Mod-2) are not linked. Our data generally support the conclusion that functionally or metabolically related isozyme genes are not contiguous on mouse linkage groups.This investigation was supported in part by Public Health Service General Research Support Grant GM-09966 and in part by Public Health Service Training Grant 5T01 HD-00032-07 from the National Institute of Child Health and Human Development, and by Atomic Energy Commission contract AT(30-1)-3671.     

Genetic control of mitogen-induced B-cell hyperproliferation in SM/J mice

Previous studies have shown that B cells from SM/J mice exhibit hyperproliferative responsiveness to several bacterial-derived B-cell mitogens. This hyperresponse trait was found to be under autosomal, polygenic control by non-H-2 genes. We have now estimated the number of genes involved by statistical analysis of the proliferative responses of splenocytes from SM/J and low-responder C57BL/6J strains, and progeny from the (B6 × SM)F₁, F₂ and (F₁ × B6) crosses. The number of loci involved was ascertained using two different statistical approaches. An estimate of two loci was determined using chi-squared statistics. The second approach, based on an additive model in the natural log scale, also pointed to a lower bound of two genes. We conclude that the hyperresponse to B-cell mitogens in SM/J mice is determined by two autosomal genes which are not linked to the H-2 major histocompatibility complex.Abbreviations used in this paper LPS a bacterial lipopolysaccharide - AVIS a mitogenic preparation from Actinomyces viscosus - B6 C57BL/6J mice - ¹²⁵IUdR ¹²⁵Iodo-deoxyuridine     

A gene apparently determining the extent of sialylation of lysosomal α-mannosidase in mouse liver

Organ-specific electrophoretic heterogeneity of lysosomal -mannosidase has been observed within individual strains of inbred mice. Polymorphism between C57BL/6J and CBA/J for liver lysosomal -mannosidase is determined by a single genetic locus on chromosome 5 and appears to be the result of differences in sialylation of the lysosomal enzyme. Two different patterns of expression of development of the liver electrophoretic forms have been observed.Supported in part by Grant GM-19521 from the U.S. Public Health Service. One of the authors (M.D.) was supported in part from USPHS Grant TAO-CA05016.     

A new locus regulating the expression of the Ldh-2 gene in mouse liver

Patterns of lactate dehydrogenase (LDH) isozymes of tissues from various mouse strains were examined. An interstrain polymorphism for LDH isozymes of liver was established. One phenotype (CBA/Lac and AKR/J mice) yielded a five-banded LDH pattern, another phenotype (DBA/1J, DBA/2J, C57BL/6J and C3H/He) showed a three-banded one. Immunochemical evidence was obtained indicating that differences in the LDH pattern are mainly due to different contents of the B subunit of LDH. Linkage tests indicated that the locus Ldr-2 determining the amounts of the LDH B subunit in mouse liver tissue is located in chromosome 6, 19 ± 4.1 cm away from the earlier described Ldr-1 locus. The effect of locus Ldr-2 is strictly tissue-specific; it is manifest only on days 6–8 after birth.     

Control of liver tyrosine aminotransferase expression: Enzyme regulatory studies on inbred strains and mutant mice

Studies on the genetic mechanisms in control of mouse liver tyrosine aminotransferase expression were of three general types: (1) studies on strain variance in endogenous enzyme activity and of various factors affecting the basal enzyme level, (2) purification of the enzyme and studies of its properties, and (3) studies of strain variance in enzyme regulation dealing primarily with glucocorticoid induction and with the starvation-induced enzyme adaptation. Tyrosine aminotransferase (l-tyrosine: 2-oxoglutarate aminotransferase, E.C. 2.6.1.5) was purified 400 to 600-fold from livers of C57BL/6J and DBA/2J inbred mice. Several of the properties of the mouse liver enzyme were similar to those known for the rat liver enzyme although the apparent K _m (l-tyrosine) was lower, calculated at 6.25×10^–4 M. Disc gel electrophoresis of the enzyme from 105,000 g supernatant fluid after induction by hydrocortisone indicated three bands of enzyme activity with strain variance in electrophoretic mobility between the C57BL/6J and DBA/2J mice. The administration of glucose to fasting C57BL/6J mice repressed the starvation-induced increase in enzyme activity, but did not prevent the hydrocortisone induction of enzyme activity. DEAE-cellulose chromatography of purified enzyme from fasting DBA/2J and C57BL/6J mice which had been labeled in vivo with C ¹⁴ -l-leucine revealed strain differences in the elution patterns for both enzyme activity and radioactivity. Two peaks of enzyme activity were detected in the enzyme preparations from fasting mice. The marked strain variance in the enzyme activity and the quantity of radioactivity associated with the first enzyme peak may indicate differential rates of protein turnover for different isozymic forms of tyrosine aminotransferase. Flumethasone, a potent difluoro synthetic glucocorticoid, was used in studies on the hormonal regulation of tyrosine aminotransferase in obese mutant mice of the C57BL/6J-ob strain. The obese mice are relatively insensitive to the action of adrenal glucocorticoids to cause liver enzyme induction.This paper was presented at a symposium entitled Genetic Control of Mammalian Metabolism held at The Jackson Laboratory, Bar Harbor, Maine, June 30–July 2, 1969. The symposium was supported in part by an allocation from NIH General Research Support Grant FR 05545 from the Division of Research Resources to The Jackson Laboratory.This investigation was supported in part by an allocation from the NIH General Research Support Grant FR 05545 from the Division of Research Resources to The Jackson Laboratory and in part by Institutional Grant IN-19 from the American Cancer Society to The Jackson Laboratory.     

A new variant of serum leucine aminopeptidase in the mouse: Its development and possible regulation

Serum leucine aminopeptidase (LAP) isozymes were compared in four strains of inbred mice during postnatal development, adult life, and pregnancy. In pregnancy, no changes in the maternal serum LAP pattern were observed, in contrast to human studies. One strain, DD/S, differs from the other three in serum LAP. Polymorphism in serum LAP has not been previously described in the mouse. Neonatal DD/S mice exhibit a single band of serum LAP upon starch gel electrophoresis; however, between 14 and 18 days of age, two distinct bands appear, which persist throughout adult life. In the strains C57BL/6J, BALB/cJ, and DBA/2J there is a single band of activity at all stages. Crosses and backcrosses between DD/S and C57BL/6J show that the double-band variant is inherited as an autosomal recessive. The variant is independent of both the supernatant malic enzyme (Mod-1) and the intestinal LAP (Lap-1) loci, which are known to be linked on chromosome 9. The serum LAP variant is linked to an intestinal alkaline phosphatase variant. The presence of a separate structural gene is suggested by the genetic independence of the serum LAP variant from Lap-1. Also, the two serum LAP bands of DD/S are not interconverted by treatment with neuraminidase, -mercaptoethanol, or heat or by mixing the sera of DD/S and C57BL/6J prior to electrophoresis. The level of serum LAP activity in DD/S is approximately twice that in C57BL/6J. While these observations imply two structurally distinct proteins, the absence of any trace of the second LAP band in the heterozygote strongly suggests that the LAP variant protein is not the result of a separate structural gene. Intestinal LAP in DD/S migrates with the same electrophoretic mobility as the serum LAP variant, implying that the variant might originate in the intestine and its appearance in the serum be modulated by some factor at an unlinked locus.This work was supported by National Institutes of Health Grant RR08117.     

Separation of T and B lymphocytes from various mouse strains by density gradient electrophoresis

T and B mouse spleen lymphocytes were separated by density gradient electrophoresis on the basis of their surface charge. In all strains examined, the T lymphocytes were found in the high mobility fractions and the B in the low. The T and B cells were separated completely in most fractions, with some overlapping in the middle. Significant differences were found in the electrophoretic distribution profiles between the strains: C57BL/6j, C57BL/10j, (BALB/cXC57BL/6j)F₁, and all the following: B₆·C-H-2^d/cBy (congenic to C57BL/6j), BALB/c, CBA/H/T6j, C57BL/10Sn, and C3H. The C57BL/6j and the (BALB/cXC57BL/6j)F₁ cells appear more heterogeneous as far as electrophoretic mobility is concerned. Almost all the other strains give two major peaks. Moreover, the high mobility areas are less populated in the C57BL/6j and the (BALB/cXC57BL/6j)F₁ animals than in all the others. The above differences were found consistently when cells prepared by different methods were electrophoresed. It is concluded that the surface charge of lymphocytes may be genetically determined. Possible dependency on the H-2 complex or non-H-2 areas is discussed.     

A second gene affecting the sialylation of lysosomal α-mannosidase in mouse liver

We have previously reported on a mouse liver-specific genetic polymorphism associated with altered sialylation of lysosomal a-mannosidase. A second electrophoretic polymorphism for liver lysosomal a-mannosidase has now been found and characterized. This variation, between SWR/J and SM/JCv inbred mice, is determined by a single genetic locus (Map-2) on chromosome 17 and appears to be the result of further differences in sialylation of the lysosomal enzyme. The Map-2 gene appears to affect the processing of liver, spleen, and lung lysosomal a-mannosidase, whereas the Map-1 gene appears to be specific to the processing of liver lysosomal a-mannosidase (Dizik and Elliott, 1977). The more negatively charged electrophoretic liver phenotype (MA-A) characteristic of the SM/JCv strain is recessive to the phenotype (MA-B) characteristic of the SWR/J strain. In contrast, at the Map-1 locus, the more negatively charged phenotype is dominant. The electrophoretic pattern of development of the liver enzyme from SM/JCv mice is described.This work was supported in part by Grant GM-19521 from the U.S. Public Health Service. One of the authors (M. D.) was supported in part by USPHS Grant TAO-CA05016.In partial fulfillment of the requirements for the Ph.D. degree.     

Genetics of Murine Liver and Kidney Arylsulfatase B

Mice from 12 inbred strains were surveyed for variation of kidney and liver arylsulfatase levels. Kidney variation was due to differences in the activity of arylsulfatase B. Twofold higher activities of arylsulfatase B in SWR/J kidney compared to A/HeJ kidney were determined by an autosomal gene which may be identical to the structural gene for arylsulfatase B since the SWR/J enzyme was more heat-stable than the A/HeJ enzyme. C57BL/6J mice possessed two-fold higher liver arylsulfatase levels than did A/HeJ mice. The major portion of this variation could be attributed to differences in arylsulfatase B, and appeared to be inherited in autosomal fashion. Although some evidence supports the existence of a major locus influencing liver arylsulfatase activity, this must be substantiated by further studies. Whatever the nature of the genetic factors involved, they do not appear to involve structural genes since no differences were discernible between the enzymes of the two strains relevant to Km, heat stability, electrophoretic mobility, pH optimum, activation energy, or response to several inhibitors. Furthermore, the rank ordering of strains on the basis of kidney arylsulfatase activity differed markedly from that which pertained to liver activity. Kidney arylsulfatase levels, but not brain or liver arylsulfatase activities, appear subject to androgenic influences.     

Biochemical genetics of a new glucosephosphate isomerase allele (Gpi-1 c) from wild mice

We have found a new allele at the structural locus for glucosephosphate isomerase (called Gpi-1 ^c ) in a population of wild mice. The Gpi-1 ^c allele codes for an enzyme of greater cathodal electrophoretic mobility than either the Gpi-1 ^a or Gpi-1 ^b alleles found in the wild and in the SM/J and C57BL/6J inbred strains. Mice homozygous for Gpi-1 ^c have erythrocyte enzyme activity reduced to 33% of normal levels, altered pH profile, lowered heat stability, and normal K _m 's when compared with SM/J and C57BL/6J mice. The activity of the enzyme in brain, liver, and kidney is not so markedly lowered, although the electrophoretic mobility, pH profile, and heat stability are altered in these tissues. Deficiencies of erythrocyte glucosephosphate isomerase in man, to this level, can cause severe hemolytic anemia. Homozygotes for Gpi-1 ^c show only mild hematological symptoms. The frequency of Gpi-1 ^c in wild populations of mice is discussed and the occurrence of a further rare allele Gpi-1 ^d is reported.This work was supported by M.R.C. grants to Professor R. J. Berry and Dr. H. Kacser, whom we should also like to thank for much help and useful discussion.     

Genetic studies of murine catalase: Regulation of multiple molecular forms of kidney catalase

Starch gel electrophoresis of kidney catalase in inbred strains C3H and C57BL/6, their F₁ hybrid, and first and second backcross generations demonstrated that single-component (type A) v. multiple-component (type B) electrophoretic patterns are controlled by a single locus. The type A electrophoretic pattern is dominant. Twenty-five inbred strains of mice were classified according to their kidney catalase electrophoretic pattern. The data indicate that the segregating genetic factor determines a specific substance in the type A kidney which affects the electrophoretic mobility of catalase. A comparison of the F₁ hybrid enzyme with a 1:1 mixture of C3H and C57BL/6 enzyme showed that the alteration of electrophoretic mobility is the result of posttranslational modification of the catalase molecule. An association of kidney catalase electrophoretic pattern and the H-2 ^k haplotype indicates that the locus controlling the electrophoretic pattern is most likely located on chromosome 17 in close proximity to the H-2 complex.     

Purification and characterization of mouse alcohol dehydrogenase from two inbred strains that differ in total liver enzyme activity

Alcohol dehydrogenase activity in mouse liver homogenate-supernatants is 1.7 times greater in the C57BL/10 strain than in the BALB/c strain, regardless of whether activity is expressed in units per gram liver, total liver, or milligram DNA. The K _m values for ethanol and NAD⁺, approximately 0.4 and 0.03mm, respectively, of enzyme purified from both strains are similar. Moreover, the K _i for NADH, 1 µm, the pH optimum for ethanol oxidation, 10.5, and the V _max for ethanol oxidation, 160 min^–1, for ADH from the C57BL/10 and BALB/c strains are similar. Therefore, the difference in ADH activity in the two strains cannot be due to differences in the catalytic properties of the enzyme. The electrophoretic and isoelectric focusing patterns and two-dimensional tryptic peptide maps of the purified enzyme from both strains are identical. Thus the amino acid sequences of enzyme from C57BL/10 and BALB/c mice must also be identical or very similar. The difference in ADH activity in the two strains is most likely the result of genetic differences in the content of ADH protein in liver.Supported by NIAAA Grant AA 04307.     

Lactate dehydrogenase isozymes in xenotropic virus producing mice

Lactate dehydrogenase (LDH; E.C. 1.1.1.27) isozymes were compared in three inbred strains of mice, and two strains of wild mice, as well as the F1 hybrids and other genetic crosses involving two of the inbred strains. The strains examined were NZB/B1NJ, 129/J and C57BL/6J, Mus musculus molossinus and M. musculus castaneus. Genetic crosses were made between the xenotropic virus-producing NZB and the non-virus producing 129/J mice. Tissue specificity of LDH in these strains was studied using homogenates of kidney, liver, spleen and thymus. Polymorphism of the enzyme was studied by agarose gel electrophoresis. Enzyme polymorphism in the tissues of NZB and 129/J has not been previously reported. The liver and spleen tissues of 129/J showed the absence of LDH-1 and LDH-2 isozymes. Thymic homogenates of NZB showed a lack of expression of LDH-1, LDH-2 and LDH-3 isozymes. The F1, F2 and the backcross progeny from genetic crosses involving NZB, and 129/J mice showed an isozyme pattern more similar to the non-virus-producing 129/J strain than the virus-producing NZB. Evidence of genetic regulation at the LDH-B subunit appears to be the reason for the differential expression of the isozymes in NZB and 129/J strains. The other inbred strain of mice, C57BL/6J, also showed a greater similarity to the 129/J strain than NZB. The two strains of wild mice were similar in their expression of LDH-isozymes between each other and to the 129/J strain, with respect to the liver and spleen tissues.     

Sex-limited genetic variation in a mouse salivary protein

This report describes a gene which influences the electrophoretic mobility of a protein in the salivas of adult mice. Three categories of phenotype have been observed: the two single-banded types, F (Fast) and S (Slow), and the two-banded type, SF (Slow-Fast), with the two bands represented in varying proportions. All females, regardless of age or strain, and all males before puberty show only the F phenotype. Males of the BALB/c and C57BL/6J strains show the F phenotype throughout puberty and adult life, whereas males of the C3H/St and C57BL/KsJ strains show the SF phenotype in puberty and the S phenotype in adult life. We have designated this variation the sex-limited saliva pattern (Ssp). The results from genetic crosses indicate that the variation among the strains is determined by an autosomal locus, Ssp, with two alleles, Ssp ^S andSsp ^F ,where Ssp ^S is dominant to Ssp ^F .Testosterone treatment can accelerate the acquisition of the S type in males of the strains C3H/St and C57BL/KsJ and also induces that phenotype in C3H/St females and C57BL/6J males. Thus it appears that the observed strain-specific differences reflect a genetic variation in androgen levels and/or androgen sensitivity rather than variation in a structural gene.This study was supported in part by PHS Research Grant 5 RO1 AM21177 and by the Indiana University Human Genetics Center (PHS PO1 GM21054). The preliminary work was done during a 1-month visit by RCK to the Institute of Ecology and Genetics which was supported by the University of Aarhus. This is publication No. 80-18 from the Department of Medical Genetics. RCK was supported by PHS Career Development Award 1 KO4 AM00284. SRD was supported by PHS General Medical Training Grant T32 GM07468.     

Variation in Type 2 Diabetes-Related Phenotypes among Apolipoprotein E-Deficient Mouse Strains

We recently have found that apolipoprotein E-deficient (Apoe^-/-) mice with the C57BL/6 background develop type 2 diabetes when fed a Western diet for 12 weeks. In the present study we constructed multiple Apoe^-/- mouse strains to find diabetes-related phenotyptic variations that might be linked to atherosclerosis development. Evaluation of both early and advanced lesion formation in aortic root revealed that C57BL/6, SWR/J, and SM/J Apoe^-/- mice were susceptible to atherosclerosis and that C3H/HeJ and BALB/cJ Apoe^-/- mice were relatively resistant. On a chow diet, fasting plasma glucose varied among strains with C3H/HeJ having the highest (171.1 ± 9.7 mg/dl) and BALB/cJ the lowest level (104.0 ± 6.6 mg/dl). On a Western diet, fasting plasma glucose rose significantly in all strains, with C57BL/6, C3H/HeJ and SWR/J exceeding 250 mg/dl. BALB/cJ and C3H/HeJ were more tolerant to glucose loading than the other 3 strains. C57BL/6 was sensitive to insulin while other strains were not. Non-fasting blood glucose was significantly lower in C3H/HeJ and BALB/cJ than C57BL/6, SM/J, and SWR/J. Glucose loading induced the 1st and the 2nd phase of insulin secretion in BALB/cJ, but the 2nd phase was not observed in other strains. Morphological analysis showed that BALB/cJ had the largest islet area (1,421,493 ± 61,244 μm²) and C57BL/6 had the smallest one (747,635 ± 41,798 μm²). This study has demonstrated strain-specific variations in the metabolic and atherosclerotic phenotypes, thus laying the basis for future genetic characterization.     

Separation of T and B lymphocytes from various mouse strains by density gradient electrophoresis.

T and B mouse spleen lymphocytes were separated by density gradient electrophoresis on the basis of their surface charge. In all strains examined, the T lymphocytes were found in the high mobility fractions and the B in the low. The T and B cells were separated completely in most fractions, with some overlapping in the middle. Significant differences were found in the electrophoretic distribution profiles between the strains: C57BL/6j, C57BL/10j, (BALB/cXC57BL/6j)F1, and all the following: B6.C-H-2d/cBy (congenic to C57BL/6j), BALB/c, CBA/H/T6j, C57BL/10Sn, and C3H. The C57BL/6j and the (BALB/cXC57BL/6j)F1 cells appear more heterogeneous as far as electrophoretic mobility is concerned. Almost all the other strains give two major peaks. Moreover, the high mobility areas are less populated in the C57BL/6j and the (BALB/cXC57BL/6j)F1 animals than in all the others. The above differences were found consistently when cells prepared by different methods were electrophoresed. It is concluded that the surface charge of lymphocytes may be genetically determined. Possible dependency on the H-2 complex or non-H-2 areas is discussed.