Elizabeth S. Russell

Hereditary Anemias of the Mouse: A Review for Geneticists*

Publisher Summary This chapter discusses the formal genetics of mouse anemias and their significance for an analysis of patterns of mammalian gene action. It also describes normal hemopoietic development, homeostasis, and hemoglobin polymorphism. Anemias are classified into five categories—(1) anemias of maturation arrest, (2) anemias involving defects in iron utilization, (3) anemias involving greatly reduced erythrocyte life-span, (4) hemoglobinopathies, and (5) anemias almost secondary to genetically induced defects. During the total life of a mouse, including prenatal development, hemopoiesis takes place in four different sites. Although hemopoiesis continues in the liver until birth and for a brief time thereafter, hemopoiesis (largely myelopoiesis) commences in the spleen on fetal day 15 or 16 and in the marrow around the time of birth. Hematologically normal adult mice from many different inbred strains regularly produce more than one kind of hemoglobin. There is a widespread genetic polymorphism at both the Hba locus, determining the α-globin structure and the Hbb locus, determining the β-globin structure, and both the loci involve considerable genetic complexity.

A DEVELOPMENTAL CHANGE IN HEMOGLOBINS CORRELATED WITH AN EMBRYONIC RED CELL POPULATION IN THE MOUSE.

Abstract Two distinct populations of erythrocytes have been demonstrated in C57BL 6J fetal mice. Analyses of cell counts and smears performed with blood taken from fetuses within the gestational age range 12–16 days indicate that the first cell population (large, nucleated, and presumably of yolk sac origin) dominates the peripheral blood picture at 12 days of gestation, while the second (smaller, nonnucleated) reaches prominence at 15 days. Starch gel electrophoresis of hemoglobin preparations made from the blood cells of 12–16-day C57BL 6J fetuses reveals the presence of at least three heme-containing components that are not found in adult preparations. It may also be seen that the period 12–16 days is one in which the numbers and concentrations of these additional components undergo change. Analysis of the relative concentration of such fetal components by means of starch gel and block over the gestational period 12–16 days indicates that they are associated with the cells of the first population.

Comparison of Normal Blood Picture of Young Adults from 18 Inbred Strains of Mice

Summary (1) Erythrocyte count, hematocrit determination, hemoglobin content, reticulocyte percentage, total leukocyte count, and proportion of granulocytes were determined in the blood of 2 to 3 month old virgin males and females of 18 different inbred strains. The means and standard errors for each determination are given for each strain. (2) Although there was considerable overlap among the strains, it was possible by analysis of variance to show that there were significant genetic differences among the strains in factors affecting erythrocyte number (as shown both in count and hematocrit), and mean erythrocyte volume (one case only), total leukocyte count, and proportion of granulocytes. (3) Mean total leukocyte count for a strain was negatively correlated with proportion of granulocytes. (4) In this data, the observed strain differences do not appear to be related to differences in other known physiological characteristics.

Proof of whole-cell implant in therapy of W-series anemia.

In mice one particular type of severe hereditary macrocrtic anemia (genotype W/WV) can be cured regularly by the injection of hemopoietic cells from adult marrow or fetal liver of normal (+/+) donors (1). When this happens the circulating erythrocytes shift from a low mean number (6-7 X lo6 RBC/mm3) and large mean cell volume (mean, 55-70 p3) to a high mean number (l&11 X lo6 RBC/mm3) and smaller mean cell volume (40-45 p3) characteristic of adult normal (+/+) mice. Recipients retain these normal levels through the remainder of their lifetimes (2). Therapy of this sort, through injection of normal hemopoietic cells, has been used extensively in analysis of W-series gene action (3). In our laboratory it has been effective only when tissues of donor and recipient were highly histocompatible, though not necessarily identical (4), an observation which indicates the importance of at least short-term survival of the injected cells in successful experiments. Seller and Polani (5) succeeded in curing small numbers of WV/WV anemic mice with normal hemopoietic liver cells from fetuses from unrelated inbred strains. From the description of the genetic origin and maintenance of their WV/WV mice, it appeared to us possible that histocompatibility genes

Inherited Electrophoretic Hemoglobin Patterns among 20 Inbred Strains of Mice

The hemoglobin from mice of six inbred strains is of the single-spot electrophoretic type, and that from 14 inbred strains is of the diffuse type. No selective advantage is apparent for either type. The distribution among strains shows some relation to the history of the development of the strains.

Implantation of normal blood-forming tissue in genetically anemic mice, without x-irradiation of host.

Summary Successful implantation, without x-irradiation or other pretreatment of host, of isologous blood forming tissue from normal (ww) mouse fetal liver in viable severely anemic recipients (20 of 24 adult WW v mice, 9 of 14 juvenile WW v mice) and in lethally anemic recipients (4 of 15 juvenile WW mice) has been demonstrated. Criteria of success were permanent increase in rbc/mm3 to near-normal levels, and decrease of mean cell volume from macrocytic to normocytic levels. These changes appeared in WW v adult anemic hosts longer after cell injection than in similar transplant experiments with WW v hosts subjected to 200-r whole-body irradiation. These findings fit well with the hypothesis of competition between slow-acting indigenous blood forming tissue of genetically anemic hosts and initially small implants of rapidly functioning blood forming tissue from genetically normal donors. If methods for circumventing homografts can be found, cell implantation may be generally useful for therapy of genetic defects in erythropoiesis.

New genetically homogeneous background for dystrophic mice and their normal counterparts.

A new type of genetically homogeneous dystrophic and comparable normal mice, from an F1 hybrid cross between 129/Re-dy and C57BL/6J-dy, is now available as a result of a special breeding program. The clinical manifestations in these F1 hybrid dystrophics correspond closely with those observed in 129/Re-dydy mice, and they give completely comparable results on a variety of research tests. They are, however, considerably healthier than previously available dystrophics, with a growth rate closer to normal and a greatly increased life-span.

Evidence on Inheritance of Muscular Dystrophy in an Inbred Strain of Mice Using Ovarian Transplantation.

Summary 1. Critical evidence is given which supports the hypothesis that dystrophia muscularis is inherited in strain 129 mice on a unit autosomal recessive basis. 2. Offspring were obtained from ovaries of dystrophic females transplanted to histocompatible normal hosts. The incidence of dystrophy in a large F2 population descended from these grafted ovaries is 19%. and in a large backcross population 44%. 3. Approximately 70% of the animals bearing ovarian grafts yielded graft offspring. The technic of ovarian transplantation, as modified from that of Robertson is described. 4. Using offspring of known genotype derived from transplanted ovaries, it has been possible to provide a reliable and extensive supply of dystrophic animals and normal littermates for research use.

Strain distribution and linkage relationship of a mouse embryonic hemoglobin variant.

Search for structural variants of three globin chains (x, y, z), synthesized only during mouse embryonic hematopoiesis, was carried out by electrophoretic analysis of blood from 12-day embryos, all with C57BL/6 mothers, and fathers from 115 inbred stocks selected for their diverse genetic origins. Structure of the β-chains of adult hemoglobins differed among the tested strains, with 57 carrying the Hbbsallele, 56 the Hbbdallele, and two the Hbbpallele. The search revealed no x- or z-chain variants but confirmed and extended knowledge of a previously described y-chain variant. Blood of all embryos sired by males from the 57 Hbbsstrains contained only y1-chains, while blood of all embryos sired by Hbbdor Hbbpmales contained y2-chains as well as the y1-chains inherited from their C57 BL/6 mother. The locus controlling structure of the y-chain of mouse embryonic hemoglobins is thus extremely closely linked to the locus controlling structure of adult hemoglobin β-chain, with maximum possible recombination frequency less than 0.019.

Gametic and pleiotropic defects in mouse fetuses with Hertwig's macrocytic anemia.

Pleiotropic effects on germ cell number, hematologic status, and body size are described in 12- to 15-day WBB6F1 normal (+/-) and defective (an/an) mouse fetuses, with special emphasis on gametogenesis. Differences between genotypes were apparent by Day 12. At 12 days, normal testes contained many germ cells and frequent normal mitoses, and the number of germ cells increased rapidly from Day 12 to Day 15. By contrast, 12-day an/an testes contained fewer germ cells, frequently degenerating, and many abnormal mitoses. Their number of germ cells decreased rapidly, so that almost none persisted to Day 15. Normal ovaries contained many germ cells, with much normal mitosis on Day 12 and 13, followed by meioses, but the smaller an/an ovaries contained few germ cells, with little mitosis, some meiosis, and very much degeneration. The erythrocyte counts of both normal and anemic fetuses increased approximately fourfold between 12 and 15 days, but at comparable ages, total counts were always lower in an/an fetuses than in normal littermates. At all ages, Hertwigs anemic (an/an) fetuses were somewhat smaller than their normal littermates. Although both W/Wv and Sl/Sld mice also show macrocytic anemia and germ cell failure, the great difference in etiology of their germ cell defects indicates that an/an gene action must be qualitatively different from that in either W/Wv or Sl/Sld mice.