Hairpatches, a single gene mutation characterized by progressive renal disease and alopecia in the mouse. A potential model for a newly described heritable human disorder.

A new murine mutation, hairpatches (Hpt), is on chromosome 4, 18.1 recombination units distal to brown near the interferon alpha and beta chain structural gene complex. On the inbred HPT/Le strain background, Hpt is semi-dominant, and Hpt/Hpt mice die in utero by 6 to 8 days of gestation. Such death in utero is associated with abnormalities of embryonic ectodermal derivatives. However on the (C57BL/6J x C3HeB/FeJ-a/a) segregating hybrid background, Hpt is a fully dominant mutation. HPT/Le Hpt/+ mice can be recognized by 3 to 4 days of age by patches of lightly pigmented skin. These mice show reduced numbers of hair follicles, abnormalities in hair follicle structure, and patchy absence of hair throughout life. By 2 weeks of age, abnormal hair follicle development is accompanied by thickening of the epidermis, reduction in levels of subcutaneous fat, and dermal inflammation. Progressive glomerulosclerosis, resulting in chronic kidney failure, is accompanied by increases in glomerular mesangial matrix, deposition of immune complexes, and glomerular enlargement. Scanning electron microscopic studies revealed abnormalities of podocytes including disorganization, swelling, and fusion of the foot processes. Increase in serum blood urea nitrogen levels accompanies conspicuous renal histopathologic changes. Cardiovascular changes in Hpt/+ mice are evidenced by hypertrophy of the left heart ventricle. Increased systolic blood pressure in these animals was found by 3 months of age. Anemia occurs in Hpt/+ mice by 40 weeks. The Hpt/+ mutation provides a valuable new animal model for chronic kidney disease accompanied by skin abnormalities and ventricular hypertrophy. The pathologic changes caused by this mutation are similar to those reported in affected family members with a newly described autosomal dominant human disease.

Development of plasmacytoid cells with Russell bodies in autoimmune "viable motheaten" mice.

Mice homozygous for the autosomal recessive mutation "viable motheaten" (mev) are severely immunodeficient, show polyclonal B-cell activation, and express multiple autoantibodies over a maximum life span of 25 weeks. Lymphoid tissues from these mice contain large numbers of atypical plasma cells in which discrete glycoprotein inclusions are found within the endoplasmic reticulum. Such plasma cells are termed "Mott cells," and the inclusions are called "Russell bodies." Dense accumulations of Mott cells are present in the marginal zones of the spleen and in the lymph nodes of mev/mev mice. Russell bodies in Mott cells from mev/mev mice contain immunoglobulin (Ig) as shown by immunofluorescence microscopy at the light-microscopic level and by indirect protein A-immunogold localization at the electron-microscopic level. Ultrastructural analyses reveal the presence of amorphous, lamellar, and crystalline Russell bodies. These Ig crystals have a periodicity of 150-190 A. Lymph node cell preparations which were enriched in Mott cells by velocity sedimentation failed to secrete Ig in a polyclonal reverse plaque assay. An obligate role of the thymus in Mott cell development is evidenced by the absence of Mott cells in neonatally thymectomized mev/mev mice and in mice doubly homozygous for the nude (nu) and mev mutations. These data suggest that Mott cells in mev/mev mice are thymic-dependent plasmacytoid cells resulting from chronic B-cell activation accompanied by impaired Ig secretion.

"Viable motheaten," a new allele at the motheaten locus. I. Pathology.

A new spontaneous autosomal recessive mutation has recently occurred at the motheaten (me) locus on Chromosome 6 in strain C57BL/6J mice. Homozygotes for the new allele, designated "viable motheaten" (mev), have a mean life span of 61 +/- 2.4 days, compared with only 22 +/- 1.3 days for C57BL/6J-me/me mice. Like the original motheaten mutation, the immediate cause of death in mev/mev mice appears to be severe pneumonitis associated with accumulations of macrophages, granulocytes, and lymphocytes in the lungs. However, because of its longer life span, progression of the disease in mev/mev mice is more amenable to investigation. Eosinophilic crystalline material in alveolar macrophages from mev/mev mice is associated with extravasation of erythrocytes into alveoli. These crystals are morphologically indistinguishable from hematoidin, which results from hemoglobin breakdown following uptake of erythrocytes by macrophages. Severe macrocytic hypochromic anemia with abnormalities in size and shape of erythrocytes develops by 7 weeks. A two-fold increase in peripheral leukocyte count and a five-fold increase in the percentage of neutrophils is seen by 10 weeks. Viable motheaten mice develop focal granulocytic skin lesions by 4 days of age, show depletion of cells from the thymus cortex by 4 weeks, and lack lymphoid follicles in the lymph nodes, spleen, and Peyer's patches. Excessive erythropoiesis and myelopoiesis in the spleen result in marked splenomegaly. Lymph nodes and spleens from mev/mev mice contain increased numbers of plasma cells by 3 weeks; and by 6 weeks, large numbers of atypical plasma cells with Russell bodies are evident. Development of glomerulonephritis by 10 weeks is characterized by granular depositis of immunoglobulin and complement within glomeruli. A twofold increase of blood urea nitrogen levels is present by 15 weeks. Sterility of male mev/mev mice is associated with Leydig cell depletion in the testes, lowered testosterone levels, and impaired spermatogenesis.

Hematopoietic stem cell function in motheaten mice.

Mice homozygous for the autosomal recessive mutation "motheaten" have normal numbers of multipotential hematopoietic stem cells in the bone marrow and spleen as determined by spleen colony assay. Histologic examination shows no qualitative abnormality in morphology of stem cell colonies in recipients of bone marrow or spleen cells from motheaten mice. Despite the apparently normal ontogeny, distribution, and differentiative capacity of CFU stem cells, bone marrow and spleen cells from motheaten mice fail to save congenic +/+ lethally gamma-irradiated hosts. This impaired lifesparing capacity is not due to defective self-renewal but appears to be due in part to pulmonary hemorrhage from alveolar capillaries in the gamma-irradiated hosts. Treatment of motheaten mice with 500 R gamma-irradiation followed by reconstitution with normal bone marrow cells increases the lifespan of this mutant to 10 months of age. The early onset of pneumonitis and subsequent short lifespan of motheaten mice is determined at the level of progenitor cells in the bone marrow.

Spontaneous tumors of the prostate gland in inbred strains of mice.

Spontaneous tumors of the prostate gland in the house mouse (Mus musculus) have rarely been described. In a histologic survey of prostate glands from old (greater than 700 days of age) mice, we have observed 2 primary adenocarcinomas of the prostate gland, 1 in a 1,047-day-old C57BL/6J mouse (DEH 1009) and 1 with metastases to the kidney and lungs in a 778-day-old C57BL/KsJ mouse (DEH 705C). We have also found a rhabdomyosarcoma of the prostate gland in a C57BL/6J mouse (DEH 1121C) 732 days old. The histologic characteristics of these tumors, and of the prostate glands of mice of similar ages without prostatic neoplastic involvement, including a 736-day-old CBA/CaJ mouse (DEH 849) with adenomatous hyperplasia, are described.