Volume 1, Issue 5, Pages 707-718 (April 1998) The Mouse RecA-like Gene Dmc1 Is Required for Homologous Chromosome Synapsis during Meiosis  Kayo Yoshida, Gen Kondoh, Yoichi Matsuda, Toshiyuki Habu, Yoshitake Nishimune, Takashi Morita  Molecular Cell  Volume 1, Issue 5, Pages 707-718 (April 1998) DOI: 10.1016/S1097-2765(00)80070-2

Figure 1 Immunohistochemical Localization of the DMC1 Protein in a Wild-Type Mouse Testis Immunohistochemistry was performed as described in the Experimental Procedures. (A) Cryostat sections were stained with rabbit anti-DMC1 polyclonal antibody. The cells stained in the outer layer of the tubules in stages IX-XII were leptotene-to-zygotene spermatocytes. (B) The control without the first antibody. Magnification of (A) and (B), ×200. (C) High magnification (×1000) revealed nuclear foci with anti-DMC1 antibody. Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)

Figure 2 Targeting of the Dmc1 Locus by Homologous Recombination (A) A schematic representation of the mouse Dmc1 gene. The numbered boxes (1–4) denote a 5′ noncoding exon and three coding exons. The targeting vector pTVN4 includes the pMC1 neo gene (neo) and the HSV-thymidine kinase gene (TK). The wild-type allele produced an 18 kb KpnI product, while the disrupted allele gave rise to a 13 kb band with a 5′ hybridization probe and a 5.9 kb band with a 3′ probe, respectively. (B) Southern blot analysis of representative offspring from heterozygous matings. (+/+), wild-type; (+/−) heterozygous; (−/−), homozygous Dmc1-deficient mice. The 18 kb bands are faint because of inefficient blotting of longer DNA. (C) Northern blot analysis. Poly(A)-RNA (5 μg) isolated from testes was hybridized with probes of the complete mouse Dmc1 cDNA (Dmc1 cDNA), the 3′ untranslated region of the Dmc1 cDNA (Dmc1–3′UT), and the human glyceraldehyde-3 phosphate dehydrogenase cDNA (GAPDH). The upper band of GAPDH RNA, which is specific to the postmeiotic phase (Gapd-S), disappeared in Dmc1-deficient mouse (Welch et al. 1992). (D) Western blot analysis of DMC1 protein from testis with an anti-DMC1 polyclonal antibody. Lysates from the testis (100 μg of protein equivalent in each lane) were loaded. Bands corresponding to DMC1 (37 kDa) and DMC1-D (32 kDa) are indicated. (E and F) DMC1-specific immunostaining of paraformaldehyde-fixed frozen sections of testis from 8-week-old mice of wild-type (E) and homozygous Dmc1-deficient mouse (F). Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)

Figure 3 Reproductive Organs Are Impaired in Dmc1-Deficient Mice (A) Gross appearance of each testis from a wild-type (+/+), a heterozygous (+/−), and a homozygous mouse (−/−). The testis from the Dmc1-deficient mouse was proportionally small. (B) Gross appearance of each ovary from a wild-type (+/+), a heterozygous (+/−), and a homozygous mouse (−/−). The ovary from the Dmc1-deficient mouse was small as compared with those from wild-type and heterozygous mice. (C) Weights of testes from a wild-type (+/+), heterozygous (+/−), and homozygous mouse (−/−). The mean and standard errors are indicated. The testis from Dmc1-deficient mice weighed significantly less than their wild-type littermates after 16 days of age (n≥5). (D) Dmc1-deficient mice display normal constitutive weight gain and are the same in size as are wild-type controls. Error bars represent standard errors. Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)

Figure 4 Histological Analysis of Dmc1-Deficient Testes and Ovary (A–F) Hematoxylin- and eosin-stained cross sections of testes from 8-week-old mice. (A) A section from the wild-type male testis showing the gross morphological appearance of seminiferous tubules (magnification, ×200). (B–G) Sections of testes from 8-week-old Dmc1- deficient disrupted mice. (B) Showing the absence of pachytene-diakinesis spermatocytes, round and elongating spermatids, and spermatozoa, at 200× magnification. (C–E) Typical appearances of seminiferous tubules of Dmc1-deficient mouse testes. Photos are enlarged ×1.5 from the original observation (×200). (C) The tubules are composed of many layers of spermatocytes at the leptotene and zygotene stages. (D) Numerous apoptotic cells are in the layers inside the tubules. (E) A single layer of type-B spermatogonia is the closest to the basal lamina. (F–G) Continuous sections of the Dmc1-deficient mouse testis stained with hematoxylin–eosin (F) or labeled by the TUNEL method (G); magnification, ×200. (H) The wild-type adult ovary shows the presence of oocytes at various stages of maturation forming large follicles (×100). (I) The Dmc1-deficient mouse ovary is small and no maturing follicle was observed (×100). (J) The wild-type ovary of neonatal mouse with oocytes at the dictyate stage of meiosis. The arrow shows the enlarged oocytes surrounded by follicle cells (×200). (K) The neonatal Dmc1-deficient mouse ovary, which had no oocytes at the dictyate stage inside. The apoptotic cells with condensed nuclei were detected (×200). Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)

Figure 5 Electron Micrographs of Meiotic Chromosomes Spread from Dmc1-Deficient Mouse Spermatocytes (A) An early zygotene nucleus of the wild-type mouse, in which most of the axes were univalent axial elements, and sex chromosomes were not observed. (B) A late zygotene nucleus of the wild-type with fully paired and synapsed bivalents. X and Y chromosomes were thick but not synapsed. (C–J) Nuclei of the Dmc1-deficient mouse. (C) Nucleus of the Dmc1-deficient mouse showing extensive asynapsis, despite axial element formation. (D) Nucleus with chromosome degeneration. (E–J) Higher magnification of the Dmc1-deficient mouse testis nuclei. (E) Extensive asynapsis is observed. (F) Degenerated chromosome, presumably in the process of apoptosis. (G) Partial synapsis between equal lengths of axial elements. (H) Unusual partial synapsis (arrow) is observed between nonhomologous chromosomes with clearly different lengths. (I) Synapsis formation among three nonhomologs. (J) Complex intermingled region of synapsis among several nonhomologs in the Dmc1-deficient mouse. Magnification, (A) and (J), ×1,500; (B)-(D), ×1,000; (E)-(I), ×3,500. Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)

Figure 6 Distribution of Meiotic Nuclei in Dmc1-Deficient Mouse Spermatocytes (A) The meiotic nuclei from wild-type, heterozygous, and Dmc1-deficient mice were categorized by electron microscopy, and their populations were shown as percentages. (B) The number of unusual synaptic sites in a Dmc1-deficient mouse spermatocyte nuclei were counted. Molecular Cell 1998 1, 707-718DOI: (10.1016/S1097-2765(00)80070-2)