Natural killer cell activity in murine muscular dystrophy. III. NK-sensitive myoblast cells and lack of NK activity in beige/dystrophic hybrid mice

The NK-susceptibility of dystrophic mouse myoblast cells was investigated. Spleen cells from 8- to 10-week-old normal (+/+) and dystrophic (dy2J/dy2J) male C57BL/6J mice were fractionated on Percoll density gradients and the cells at each density interface were incubated with either 51Cr-labeled YAC-1 or myoblast cells in a 6 hr 51Cr-release assay. Myoblast target cells were obtained from either heterozygous (+/dy2J) or homozygous (dy2J/dy2J) muscle cultures or a transformed tetraploid myoblast line (M14D2). The data indicate that the interface between the 50 and 60% (1.060-1.075 g/ml) Percoll density fractions of spleen cells from either normal or dystrophic mice contains the largest proportion of asialo GM-1 positive and NK-1 positive cells displaying NK activity. Myoblast cells from either heterozygous (phenotypically normal) or homozygous dystrophic mice were not significantly different in susceptibility to NK-mediated lysis by Percoll enriched normal or dystrophic mouse NK cells. However, dystrophic mouse spleen cells had the highest NK activity against both myoblast targets as compared with normal mouse spleen cells. The transformed myoblast cell line, M14D2, was significantly less susceptible to NK-mediated lysis by dystrophic mouse spleen cells when compared with freshly cultured myoblast target cells. Target cell binding studies revealed that conjugate forming cells from the 50% Percoll density interface of dystrophic mouse spleen cells were approximately twofold greater than that of normal mouse spleen cells against either heterozygous or homozygous dystrophic mouse myoblast targets. Cold target inhibition studies revealed that the natural killing of dystrophic mouse myoblast cells was due to a YAC-1 reactive NK cell. Breeding experiments between C57BL/6J homozygous "beige" (bgJ/bgJ) mutant mice and dystrophic (dy2J/dy2J) mice produced beige/dystrophic hybrid mice which displayed clinical symptoms of the dystrophy process by 3 to 4 weeks of age. Spleen cells from these hybrid mice showed no significant differences in NK activity against YAC-1 target cells when compared with homozygous beige mice. Taken together, these results demonstrate the first reported evidence that murine myoblasts are susceptible to NK-mediated lysis. In addition, the data indicate that although dystrophic mouse NK cells recognize myoblast cells as targets, the NK cell studies with the beige/dystrophic hybrid mice do not indicate a direct in vivo role for NK cells in the dystrophy process.     

Molecular feature of the nerve growth factor in human serum

High molecular weight binding components which bind [¹²⁵I] mouse β nerve growth factor exist in human serum. The binding of β nerve growth factor to the serum components was inhibited at alkaline condition. After gel filtration of human serum on a Sephadex G-150 column at neutral condition, the nerve growth factor-like immunoreactivity was observed in only one peak, differing from the high molecular weight serum components. However, at alkaline condition two peaks with nerve growth factor-like immunoreactivity appeared; one was almost at the position observed at neutral pH, and the other was a new peak eluted approximately to the column volume. these results suggest that there are at least two nerve growth factor-like molecules in human serum and most of the nerve growth factor in the serum exists in a complex form associated with serum components with high molecular weight.     

p53-Knockout Mice Are Protected Against the Long-Term Effects of Methamphetamine on Dopaminergic Terminals and Cell Bodies

Abstract: p53-knockout mice provide a useful model to test the role of p53 in the neurotoxic effects of drugs in vivo. To test the involvement of p53 in methamphetamine (METH)-induced toxicity, wild-type mice, as well as heterozygous and homozygous p53-knockout male mice, were administered four injections of three different doses (2.5, 5.0, and 10.0 mg/kg) of the drug given at 2-h intervals within the space of 1 day. METH caused a marked dose-dependent loss of dopamine transporters in both the striatum and the nucleus accumbens of wild-type mice killed 2 weeks after drug administration. However, this METH-induced decrease in dopamine transporters was attenuated in both homozygous and heterozygous p53-knockout mice, with homozygous animals showing significantly greater protection. The possibility for p53 involvement in METH-induced toxicity was also supported by the observation that METH caused marked increases in p53-like immunoreactivity in the striata of wild-type mice and very little change in heterozygous p53-knockout mice, whereas no p53-like immunostaining was detected in the homozygous p53-knockout mice. Further support for p53 involvement was provided by the fact that METH treatment caused significant decreases in dopamine transporter mRNA and the number of tyrosine hydroxylase-positive cells in the substantia nigra pars compacta and the ventral tegmental area of wild-type but not homozygous p53-knockout mice killed 2 weeks after cessation of METH administration. These results provide concordant evidence for a role of the tumor suppressor, p53, in the long-term deleterious effects of a drug acting on brain dopamine systems.     

Genetic Expression of Cyclic GMP Phosphodiesterase Activity Defines Abnormal Photoreceptor Differentiation in Neurological Mutants of Inherited Retinal Degeneration

We have examined cyclic GMP concentrations, guanylate cyclase activities, and cyclic GMP phosphodiesterase (PDE) activities in developing retinas of congenic mice with different allelic combinations at the retinal degeneration (rd) and retinal degeneration slow (rds) loci. Although guanylate cyclase activities were found to be uniformly low in the mutant retinas, striking differences in PDE activity and cyclic GMP levels were observed in retinas of the various genotypes. Homozygous rds mice, which lack receptor outer segments, showed reduced retinal PDE activity and cyclic GMP concentration in comparison to normal animals. In heterozygous rds/+ mice with abnormal outer segments, the levels were intermediate. In retinas of homozygous rd mice, PDE activity was lower than in rds retinas and cyclic GMP levels were much higher. In mice homozygous for both rd and rds genes, retinal PDE activities were even lower than in single homozygous rd mice; the cyclic GMP level reached the same high value as in the rd animals, persisted for a longer time at this high level, and did not correlate with the rate of photoreceptor cell loss. Thus, a marked variation in PDE activity appears to be the major manifestation of abnormal outer segment differentiation and eventual degeneration of photoreceptor cells in these neurological mutants. An increased cyclic GMP level seems to be an essential corollary in the expression of the rd gene even in the absence of outer segments, but it appears unlikely that an abnormally high nucleotide level in itself causes photoreceptor cell death.     

Mouse models of fukutin-related protein mutations show a wide range of disease phenotypes

Dystroglycanopathies are characterized by a reduction in the glycosylation of alpha-dystroglycan (α-DG). A common cause for this subset of muscular dystrophies is mutations in the gene of fukutin-related protein (FKRP). FKRP mutations have been associated with a wide spectrum of clinical severity from severe Walker–Warburg syndrome and muscle–eye–brain disease with brain and eye defects to mild limb–girdle muscular dystrophy 2I with myopathy only. To examine the affects of FKRP mutations on the severity of the disease, we have generated homozygous and compound heterozygous mouse models with human mutations in the murine FKRP gene. P448Lneo+ and E310delneo+ mutations result in severe dystrophic and embryonic lethal phenotypes, respectively. P448Lneo+/E310delneo+ compound heterozygotes exhibit brain defects and severe muscular dystrophies with near absence of α-DG glycosylation. Removal of the Neo^r cassette from the P448Lneo+ homozygous mice eliminates overt brain and eye defects, and reduces severity of dystrophic phenotypes. Furthermore, introduction of the common L276I mutation to generate transgenic L276Ineo+ homozygous and L276Ineo+/P448Lneo+ and L276Ineo+/E310delneo+ compound heterozygotes results in mice displaying milder dystrophies with reduced α-DG glycosylation and no apparent brain defects. Limited sampling and variation in functionally glycosylated α-DG levels between and within muscles may explain the difficulties in correlating FKRP expression levels with phenotype in clinics. The nature of individual mutations, expression levels and status of muscle differentiation all contribute to the phenotypic manifestation. These mutant FKRP mice are useful models for the study of disease mechanism(s) and experimental therapies.     

Nras overexpression results in granulocytosis, T-cell expansion and early lethality in mice

NRAS is a proto-oncogene involved in numerous myeloid malignancies. Here, we report on a mouse line bearing a single retroviral long terminal repeat inserted into Nras. This genetic modification resulted in an increased level of wild type Nras mRNA giving the possibility of studying the function and activation of wild type NRAS. Flow cytometry was used to show a variable but significant increase of immature myeloid cells in spleen and thymus, and of T-cells in the spleen. At an age of one week, homozygous mice began to retard compared to their wild type and heterozygous littermates. Two weeks after birth, animals started to progressively lose weight and die before weaning. Heterozygous mice showed a moderate increase of T-cells and granulocytes but survived to adulthood and were fertile. In homozygous and heterozygous mice Gfi1 and Gcsf mRNA levels were upregulated, possibly explaining the increment in immature myeloid cells detected in these mice. The short latency period indicates that Nras overexpression alone is sufficient to cause dose-dependent granulocytosis and T-cell expansion.     

Evaluation of an antisense RNA transgene for inhibiting growth hormone gene expression in transgenic rats

We compared the levels of growth hormone (GH) mRNA in the pituitary, plasma GH concentration, and altered phenotype in rats heterozygous and homozygous for an antisense RNA transgene targeted to the rat GH gene, with those in nontransgenic rats. We initially investigated whether the transgene promoter, which is connected to four copies of a thyroid hormone response element (TRE) that increases promoter activity, affected in vivo transgene expression in the pituitary of the transgenic rats. Plasma GH concentration correlated negatively with T, injection in surgically thyroidectomized heterozygous transgenic rats. There was a reduction of about ?35–40% in GH mRNA levels in the pituitary of homozygous animals compared with those in non-transgenic rats. Plasma GH concentration was significantly ?25–32 and ?29–41% lower in heterozygous and homozygous transgenic rats, respectively, compared with that in nontransgenic animals. Furthermore, the growth rates in homozygous transgenic rats were reduced by ?72–81 and ?51–70% compared with those of their heterozygous and nontransgenic littermates, respectively. The results of these studies suggested that the biological effect of GH in vivo is modulated dose-dependently by the antisense RNA transgene. The rat GH gene can therefore be targeted by antisense RNA produced from a transgene, as reflected in the protein and RNA levels. © 1995 Wiley-Liss, Inc.     

Decreased G4 (10S) Acetylcholinesterase Content in Motor Nerves to Fast Muscles of Dystrophic 129/ReJ Mice: Lack of a Specific Compartment of Nerve Acetylcholinesterase?

Acetylcholinesterase (AChE; EC 3.1.1.7) activity and the distribution of its molecular forms were studied in the nervous system of normal and dystrophic 129/ReJ mice, including the sciatic-tibial nerve trunk and motor nerves to slow- and fast-twitch muscles. In normal mice, motor nerves to the slow-twitch soleus exhibited a low AChE activity together with a low level of G4 (10S form) as compared with nerves of the predominantly fast-twitch plantaris and extensor digitorum longus. In contrast, in dystrophic mice, the AChE activity as well as the G4 content of nerves to the fast-twitch muscles were low, displaying an AChE content similar to that of the nerve of the soleus muscle. In the sciatic-tibial nerve trunk, the AChE activity decreased along the nerve in an exponential mode, at rates that were similar in both conditions. However, in dystrophic mice, the AChE activity was reduced throughout the nerve length by a constant value of approximately 180 nmol/h/mg protein. Further analyses indicated that AChE in this nerve trunk was distributed among two compartments, a decaying and a constant one. The decay involved exclusively the globular forms. The activity of A12 (16S form) remained constant along the nerve and was similar in both normal and dystrophic mice. In addition, according to the equation describing the decay of AChE, the reduction in enzymatic activity observed in the dystrophic mice affected mainly G4 in the constant compartment. Brain, spinal cord, sympathetic ganglia, and serum, which were also examined, showed no remarkable differences between the two conditions in their G4 content. The AChE abnormalities that we found in nervous tissues of 129/ReJ dystrophic mice were confined to the motor system.     

Localization of nerve growth factor-like immunoreactivity in rat nervous tissue

The use of immunofluorescence with affinity-purified antibodies enabled cytological localization of nerve growth factor-like material in the rat. Immunoreactivity was observed along various nerve tracts of the foetal rat brain and spinal cord at day 15 of gestation. Longitudinal pathways in ventral and dorsal spinal cord, ventral lower brain stem, posterior commissure, retroflex fascicle and in the olfactory bulb were all positive. A weaker and more widely spread immunostaining was visible in many areas in the central nervous system. Cranial nerves were strongly immunoreactive. Neuronal perikarya in the retina and the olfactory mucosa as well as filae olfactoriae and the olfactory nerve all the way to the olfactory bulb were also positive. In sensory ganglia and peripheral nerves most immunoreactivity was confined to supporting tissues, probably including Schwann cells. In irides, the pattern of immunoreactivity was similar to that of the sensory and autonomic innervation. More intensively fluorescent material was found in regrowing nerve fibres in iris transplants. Our histochemical results suggest that nerve growth factor and/or a related protein is present in large amounts along nerve pathways in supportive tissues of the peripheral nervous system as well as in the central nervous system during early development.     

IGF-I deficient mice show reduced peripheral nerve conduction velocities and decreased axonal diameters and respond to exogenous IGF-I treatment

Although insulin-like growth factor-I (IGF-I) can act as a neurotrophic factor for peripheral neurons in vitro and in vivo following injury, the role IGF-I plays during normal development and functioning of the peripheral nervous system is unclear. Here, we report that transgenic mice with reduced levels (two genotypes: heterozygous Igf1+/- or homozygous insertional mutant Igf1m/m) or totally lacking IGF-I (homozygous Igf1-/-) show a decrease in motor and sensory nerve conduction velocities in vivo. In addition, A-fiber responses in isolated peroneal nerves from Igf1+/- and Igf1-/- mice are impaired. The nerve function impairment is most profound in Igf1-/- mice. Histopathology of the peroneal nerves in Igf1-/- mice demonstrates a shift to smaller axonal diameters but maintains the same total number of myelinated fibers as Igf1+/+ mice. Comparisons of myelin thickness with axonal diameter indicate that there is no significant reduction in peripheral nerve myelination in IGF-I-deficient mice. In addition, in Igf1m/m mice with very low serum levels of IGF-I, replacement therapy with exogenous recombinant hIGF-I restores both motor and sensory nerve conduction velocities. These findings demonstrate not only that IGF-I serves an important role in the growth and development of the peripheral nervous system, but also that systemic IGF-I treatment can enhance nerve function in IGF-I-deficient adult mice.     

Altered gene expression in liver from a murine model of hyperhomocysteinemia

Cystathionine beta-synthase (CBS) deficiency causes severe hyperhomocysteinemia and other signs of homocystinuria syndrome, in particular a premature atherosclerosis with multiple thrombosis. However, the molecular mechanisms by which homocysteine could interfere with normal cell function are poorly understood in a whole organ like the liver, which is central to the catabolism of homocysteine. We used a combination of differential display and cDNA arrays to analyze differential gene expression in association with elevated hepatic homocysteine levels in CBS-deficient mice, a murine model of hyperhomocysteinemia. Expression of several genes was found to be reproducibly abnormal in the livers of heterozygous and homozygous CBS-deficient mice. We report altered expression of genes encoding ribosomal protein S3a and methylthioadenosine phosphorylase, suggesting such cellular growth and proliferation perturbations may occur in homozygous CBS-deficient mice liver. Many up- or down-regulated genes encoded cytochromes P450, evidence of perturbations of the redox potential in heterozygous and homozygous CBS-deficient mice liver. The expression of various genes involved in severe oxidative processes was also abnormal in homozygous CBS-deficient mice liver. Among them, the expression of heme oxygenase 1 gene was increased, concomitant with overexpression of heme oxygenase 1 at the protein level. Commensurate with the difference in hepatic mRNA paraoxonase 1 abundance, the mean hepatic activity of paraoxonase 1, an enzyme that protects low density lipoprotein from oxidation, was 3-fold lower in homozygous CBS-deficient mice. Heterozygous CBS-deficient mice, when fed a hyperhomocysteinemic diet, have also reduced PON1 activity, which demonstrates the effect of hyperhomocysteinemia in the paraoxonase 1 activity.     

Large-scale phenotyping of an accurate genetic mouse model of JNCL identifies novel early pathology outside the central nervous system

Cln3(Δex7/8) mice harbor the most common genetic defect causing juvenile neuronal ceroid lipofuscinosis (JNCL), an autosomal recessive disease involving seizures, visual, motor and cognitive decline, and premature death. Here, to more thoroughly investigate the manifestations of the common JNCL mutation, we performed a broad phenotyping study of Cln3(Δex7/8) mice. Homozygous Cln3(Δex7/8) mice, congenic on a C57BL/6N background, displayed subtle deficits in sensory and motor tasks at 10-14 weeks of age. Homozygous Cln3(Δex7/8) mice also displayed electroretinographic changes reflecting cone function deficits past 5 months of age and a progressive decline of retinal post-receptoral function. Metabolic analysis revealed increases in rectal body temperature and minimum oxygen consumption in 12-13 week old homozygous Cln3(Δex7/8) mice, which were also seen to a lesser extent in heterozygous Cln3(Δex7/8) mice. Heart weight was slightly increased at 20 weeks of age, but no significant differences were observed in cardiac function in young adults. In a comprehensive blood analysis at 15-16 weeks of age, serum ferritin concentrations, mean corpuscular volume of red blood cells (MCV), and reticulocyte counts were reproducibly increased in homozygous Cln3(Δ) (ex7/8) mice, and male homozygotes had a relative T-cell deficiency, suggesting alterations in hematopoiesis. Finally, consistent with findings in JNCL patients, vacuolated peripheral blood lymphocytes were observed in homozygous Cln3(Δ) (ex7/8) neonates, and to a greater extent in older animals. Early onset, severe vacuolation in clear cells of the epididymis of male homozygous Cln3(Δ) (ex7/8) mice was also observed. These data highlight additional organ systems in which to study CLN3 function, and early phenotypes have been established in homozygous Cln3(Δ) (ex7/8) mice that merit further study for JNCL biomarker development.     

BALB/c-nu裸小鼠繁殖中杂合仔鼠剔除时间对纯合裸仔鼠生长发育的影响

目的研究屏障设施下裸小鼠繁殖生产时,在不同时间段剔除杂合仔鼠对纯合裸仔鼠的成活率及生长发育情况的影响。方法选取25窝头胎生BALB/c-nu新生裸小鼠按剔除杂合仔鼠的时间不同分成五组,以24h剔除组为对照比较纯合裸仔鼠生长发育及死亡率、离乳率的差异性,统计分析其生长发育过程中的体重增长等。结果剔除组生长发育及死亡率与对照组之间均存在差异性,其中14d剔除组和21d剔除组差异极显著。结论剔除杂合仔鼠的时间对纯合裸仔鼠的成活率及生长发育情况的有很大影响。为了保证SPF级裸鼠生长发育要求,生产繁殖出合格的实验用裸小鼠,剔除全部杂合仔鼠的最佳时间应该在新生仔鼠出生24h内,超过3d则会极大地影响纯合裸小鼠的正常生长发育。     

Haploinsufficiency in the PPARalpha and LDL receptor genes leads to gender- and age-specific obesity and hyperinsulinemia

When preparing peroxisome proliferator-activated receptor (PPAR)alpha:low-density lipoprotein receptor (LDLR) (-/-) double knockout mice, we unexpectedly found a unique gender- and age-specific obesity in the F1 generation, PPARalpha (+/-):LDLR (+/-), even in mice fed standard chow. Body weights of the male heterozygous mice increased up to about 60 g at 75 weeks of age, then decreased by about 30 g at 100 weeks of age. More than 95% of the heterozygous mice between 35- and 75-week-olds were overweight. Of interest, the obese heterozygous mice also exhibited hyperinsulinemia correlating with moderate insulin resistance. Hepatic gene expression of LDLR was lower than expected in the heterozygous mice, particularly at 50 and 75 weeks of age. In contrast, the hepatic expression of PPARalpha was higher than expected in obese heterozygous mice, but decreased in non-obese older heterozygous mice. Modulated expression of these genes may be partially associated with the onset of the hyperinsulinemia.     

Immuno-electron-microscopic localization of basic fibroblast growth factor in the dystrophic mdx mouse masseter muscle

Summary The localization of basic fibroblast growth factor (bFGF)-like immunoreactivity in the masseter muscle of dystrophic mdx mice on postnatal day 28 was investigated by immunoblot analysis and electron microscopy. Crude homogenate of the masseter muscle, when subjected to immunoblotting with a bFGF antiserum, exhibited a main band with the same molecular weight (18 kDa) as bovine bFGF. By electron microscopy, bFGF immunoreactivity was detected in small regenerating myocytes; the smaller cells were the premature myocytes, the most intense staining was the immunoreactivity within the cytoplasm. Putative precursors of the muscle cells with a few myofilaments, which were most intensely labeled with anti-bFGF, contacted each other and possibly developed into multinucleated myocytes through cell fusion. Mature myocytes with densely packed myofilaments and peripherally located nuclei did not exhibit bFGF immunoreactivity; they formed myoneural junctions with motor nerve endings immunoreactive for bFGF. Early differentiating myocytes with intense bFGF-like immunoreactivity did not make contact with immunoreactive nerve terminals. Degenerating large myocytes with a limited number of distorted and/or disrupted myofilaments exhibited electron-dense deposits in the cristae of mitochondria; these deposits were not abolished by immunoadsorption control experiments. Thus, the cell-size-dependent decrease in bFGF immunoreactivity in regenerating but not in degenerating myocytes provides a morphological basis for an autoregulatory role of bFGF in muscle regeneration. This study suggests that neuronal bFGF is not involved in initial muscle regeneration in the dystrophic mdx mouse.     

Further mapping of quantitative trait loci for postnatal growth in an inter-sub-specific backcross of wild Mus musculus castaneus and C57BL/6J mice

We performed a quantitative trait locus (QTL) analysis of eight body weights recorded weekly from 3 weeks to 10 weeks after birth and two weight gains recorded between 3 weeks and 6 weeks, and between 6 weeks and 10 weeks in an inter-sub-specific backcross population of wild Mus musculus castaneus mice captured in the Philippines and the common inbred strain C57BL/6J ( M. musculus domesticus ), to elucidate the complex genetic architecture of body weight and growth. Interval mapping identified 17 significant QTLs with main effects on 11 chromosomes. In particular, the main effect of the most potent QTL on proximal chromosome 2 increased linearly with age, whereas other QTLs exerted effects on either the early or late growth period. Surprisingly, although wild mice displayed 60% of the body size of their C57BL/6J counterparts, the wild-derived allele enhanced growth at two QTLs. Interestingly, five of the 17 main-effect QTLs identified had significant epistatic interaction effects. Five new epistatic QTLs with no main effects were identified on different chromosomes or regions. For one pair of epistatic QTLs, mice that were heterozygous for the wild-derived allele at one QTL and homozygous for that allele at another QTL exhibited the most rapid growth in all four possible genotypic combinations. Out of the identified QTLs, several showed significant sex-specific effects.     

RAPID AXOPLASMIC TRANSPORT IN DYSTROPHIC MICE

Abstract— Rapid axoplasmic transport was studied in dystrophic mice of the 129/ReJ-dy strain. Proteins transported in vivo through α-motoneurons of the sciatic nerve were labeled by injections of [³H] or [³⁵S] amino acids into the ventral horn of the lumbar spinal cord. Following an 18 h incubation, axoplasmic transport was quantitated by summing the radioactivity in the 10 mm length of sciatic nerve proximal to a ligation. Although the amount of transported radioactivity was small, transport appeared depressed when adult dystrophic mice were compared to controls. Transport was also studied in the sensory fibers of the sciatic nerve under in vitro conditions, resulting in high levels of transported radioactivity. In this system transport was strongly depressed. The severity of the deficiency varied with age, being small in animals with early clinical signs and becoming maximal (80–90%) in animals over 60 days of age. Proteins transported by adult dy/dy and +/+ animals were compared by gel electrophoresis using double-label techniques. Transport of nearly all proteins was depressed in dy/dy mice, although the possibility exists that small differences occur. The data suggest that the dystrophic state produces a significant deficiency in rapid axoplasmic transport in both motor and sensory fibers, and may interfere with transport processes in all neurons. Since rapid axoplasmic transport has been associated with membranes, the data are consistent with a general alteration of cellular membranes in dystrophic animals.     

Pattern of compensatory expression of voltage-dependent Ca2+ channel alpha1 and beta subunits in brain of N-type Ca2+ channel alpha1B subunit gene-deficient mice with a CBA/JN genetic background.

The Ca(2+) channel alpha(1B) subunit is a pore-forming component capable of generating N-type Ca(2+) channel activity. Although the N-type Ca(2+) channel plays a role in a variety of neuronal functions, alpha(1B)-deficient mice with a CBA/JN genetic background show no apparent behavioral or anatomical-histological abnormality, presumably owing to compensation by other Ca(2+) channels. In this study, we examined the mRNA expression of the alpha(1A), alpha(1C), alpha(1D), alpha(1E), beta(1), beta(2), beta(3) and beta(4) subunits in the olfactory bulb, cerebral cortex, hippocampus and cerebellum of alpha(1B)-deficient mice. We found that the mRNA expression levels of the alpha(1A), alpha(1C), alpha(1D), alpha(1E), beta(1), beta(2), beta(3) and beta(4) subunits were the same in the olfactory bulbs of wild, heterozygous and homozygous alpha(1B)-deficient mice. In the cerebral cortex, alpha(1A) mRNA in homozygous alpha(1B)-deficient mice was expressed at a higher level than in wild or heterozygous mice, but no difference in the expression levels of the alpha(1C), alpha(1D), alpha(1E), beta(1), beta(2), beta(3) and beta(4) subunits was found among wild, heterozygous and homozygous mice. In hippocampus and cerebellum, beta(4) mRNA in homozygous alpha(1B)-deficient mice was expressed at a higher level than in wild or heterozygous mice, but no difference in the expression levels of the alpha(1A), alpha(1C), alpha(1D), alpha(1E), beta(1), beta(2) and beta(3) subunits was found among wild, heterozygous and homozygous mice. These results suggest that the compensatory mechanisms differ in different brain regions of alpha(1B)-deficient mice with a CBA/JN genetic background.