Sei-ichi Kohno

The ZW sex chromosomes of Gekko hokouensis (Gekkonidae, Squamata) represent highly conserved homology with those of avian species.

Populations of the gecko lizard Gekko hokouensis (Gekkonidae, Squamata) on Okinawajima Island and a few other islands of the Ryukyu Archipelago, Japan, have the morphologically differentiated sex chromosomes, the acrocentric Z chromosome and the subtelocentric W chromosome, although the continental representative of this species reportedly shows no sex chromosome heteromorphism. To investigate the origin of sex chromosomes and the process of sex chromosomal differentiation in this species, we molecularly cloned the homologues of six chicken Z-linked genes and mapped them to the metaphase chromosomes of the Okinawajima sample. They were all localized to the Z and W chromosomes in the order ACO1/IREBP–RPS6–DMRT1–CHD1–GHR–ATP5A1, indicating that the origin of ZW chromosomes in G. hokouensis is the same as that in the class Aves, but is different from that in the suborder Ophidia. These results suggest that in reptiles the origin of sex chromosomes varies even within such a small clade as the order Squamata, employing a variety of genetic sex determination. ACO1/IREBP, RPS6, and DMRT1 were located on the Z long arm and the W short arm in the same order, suggesting that multiple rearrangements have occurred in this region of the W chromosome, where genetic differentiation between the Z and W chromosomes has been probably caused by the cessation of meiotic recombination.

Chromosomal Location and Nucleotide Sequences of 5S Ribosomal DNA of Two Cyprinid Species (Osteichthyes, Pisces)

Abstract5S ribosomal DNAs (rDNAs) from two cyprinid species, Acheilognathus tabira subsp. 1 and Cyprinus carpio, were isolated and sequenced. Tandemly arranged rDNAs were 179 bp in A. tabira and 204 bp in C. carpio. The non-transcribed spacer region elucidates the size difference of 5S rDNA between the two species. Fluorescence in-situ hybridization (FISH) localized 5S rDNAs to the short arms of two pairs of chromosomes in A. tabira and two to four pairs in C. carpio. Subsequent analysis demonstrated NORs in one pair of chromosomes in both species. Both the NOR and 5S rDNA are carried by a chromosome pair in A. tabira, but they are located on different chromosomes separately in C. carpio. Karyotype evolution by tetraploidy seems complex in cyprinid species.

A summary of cytogenetic studies on 534 cases of chronic myelocytic leukemia in Japan

Cytogenetic and clinical data on 534 patients with chronic myelocytic leukemia (CML) were collected from 10 institutions in Japan. The results of the analysis of the data were in substantial accord with those of the First International Workshop on Chromosomes in Leukemia and other published data, but certain differences were noted in the frequency of Philadelphia chromosome (Ph1)-negative cases, unusual and complex Ph1 translocations, and additional chromosome changes. Some of the findings are discussed with respect to the origin of unusual and complex Ph1 translocations, the relationship between chromosome abnormalities and survival, and geographic differences in chromosome abnormalities.

Chromosomes and causation of human cancer and leukemia. XXXIV. A case of “hypereosinophilic syndrome” with unusual cytogenetic findings in a chloroma, terminating in blastic transformation and CNS leukemia

A 47‐year‐old white male developed massive hepatosplenomegaly, a pleural effusion, leucocytosis, and a left parasternal mass following a relatively symptomfree persistent hypereosinophilia for about 5 years. Bone marrow aspiration and biopsy and peripheral blood differential showed eosinophilia and a shift to the left with immature cells. A high serum B12 vitamin level and low LAP activity were found. Biopsy of the soft tissue mass revealed a granulocytic sarcoma (chloroma) with a hyperdiploid karyotype (49,XY,+10,+15,+19,3q‐), whereas the bone marrow cells had a normal male karyotype. The patient responded temporarily to chemotherapy but eventually developed CNS leukemia and went on to terminate in a frank blastic phase. This case illustrates hypereosinophilia and a myeloproliferative syndrome characterized by a somewhat indolent chronic course evolving into “eosinophilic leukemia” and granulocytic sarcoma, CNS involvement by leukemic cells and, finally, blastic transformation. It is possible that this case represents a variant of Ph1‐negative CML to which the term “chronic eosinophilic leukemia” could be justifiably applied.

Chromosome studies in early embryogenesis

Abstract Chromosome studies were made on 520 induced abortuses randomly collected in Sapporo. The mean gestational age was 9.6 ± 2.0 weeks after the first day of the last menstrual period, and the mean maternal age was 26.6 ± 5.8 years. There were 2 cases of X monosomy and 3 cases of autosomal trisomies for C, D, and E chromosomes, respectively. In addition, 12 males with an unusually long Y chromosome, 6 cases with an enlarged short arm or satellite in one of acrocentrics, and 1 each case with a heteromorphic pair of either No. 1 or 16 were found. A high incidence (10 to 42 per cent) of chromosome breakage was noted in 9 cases. Tetraploid cells were frequently observed in 6 cases (5.5 to 16.3 per cent). The sex ratio was 95.4 (XX + X : XY = 266 : 254), showing a slight excess of females over males, though a tendency was shown that the younger the embryonic age the lower the sex ratio.

Molecular organization of 5S rDNA in bitterlings (Cyprinidae)

Molecular organization and nucleotide sequences of the 5S rRNA gene and NTS were investigated in freshwater fish, bitterlings (Acheilognathinae), including 10 species/subspecies of four genera, Acheilognathus, Pseudoperilampus, Rhodeus, and Tanakia, to understand the evolutionary trait of 5S rDNA arrays. Southern hybridization analysis revealed a general trend with tandem repeats of 5S rDNA in all the examined bitterlings. Sequence analysis demonstrated a conserved 120 bp sequence of the 5S rRNA gene and a short NTS of 56–67 bp with two distinct portions, a conserved (5′-flanking portion; at positions −1 to −38) and a variable part (3′-flanking portion), in 6 of 10 species/subspecies examined. The conserved NTS region was most likely an external promoter so far observed in various vertebrates, whereas the variable NTS region could be divided into two types due to its nucleotide polymorphisms. Molecular phylogeny using the 5S rRNA gene and NTS sequences suggested the occurrence of 5S rDNA duplication before speciation and a concerted evolution for the gene and conserved NTS regions, but a birth-and-death process to maintain the variable NTS region. Thus, the 5S rDNA in the examined bitterlings might have evolved under a mixed process of evolution.

Chromatin diminution and chromosome elimination in four Japanese hagfish species.

Cytogenetic examination of four Japanese hagfish species belonging to the order Myxinida (Eptatretus okinoseanus, E. burgeri. Paramyxine atami, and Myxine garmani) revealed differences in chromosome number between germ cells (spermatocytes and spermatogonia) and somatic cells (liver, blood, gill, and kidney). The differences in chromosome number between spermatogonia (54, 52, 48, and 16) and somatic cells (34, 36, 34, and 14) were 20, 16, 14, and 2 in E. okinoseanus, E. burgeri, P. atami, and M. garmani, respectively. The amount of DNA in a somatic cell (2C) relative to that in a germ cell (2C) averaged 54.6% (E. okinoseanus type A), 44.9% (E. okinoseanus type B), 79.1% (E. burgeri), 60.0% (P. atami), and 70.2% (M. garmani). These results clearly indicate that chromosome elimination takes place during early cleavage in the four hagfish species of Myxinida living in Japanese waters, except in the ancestral germline cells. C-banding of metaphase chromosome preparations of germline and somatic cells from each hagfish species revealed that the C-band-positive chromatin in the ancestral somatic cells had been almost completely eliminated. Three patterns of elimination of this chromatin are discussed.

Chromosomes and causation of human cancer and leukemia. XLII. Ph1-positive ALL: An entity within myeloproliferative disorders?

Abstract The clinical, survival, and cytogenetic features of 8 cases with Philadelphia chromosome (Ph 1 )-positive acute lymphoblastic leukemia (ALL) have been presented. Based on these data, and taken in conjunction with surface marker and enzymic characteristics of the leukemic cells, it is proposed that Ph 1 -positive ALL, though sharing many of the clinical and laboratory aspects of Ph 1 -negative ALL, is in some cases probably a disease of the pre-B cell type, or its close lymphoid entity, with such cell probably originating from a myeloid precursor. The reversion of Ph 1 -positive ALL to chronic myelocytic leukemia (CML) and the many common features it shares with the lymphoid blastic phase (BP) of CML, as well as the rare appearance of acute myeloblastic leukemia (AML) or myeloid features subsequent to complete remission (CR) of Ph 1 -positive ALL, when taken together indicate that Ph 1 -positive ALL is probably a disease within the myeloproliferative disorders. The cell predominating at any one moment decides the character of the disease, which may vary from ALL to CML to AML and to the BP of CML. The literature on Ph 1 -positive ALL is reviewed and tabulated and the various cytogenetic, survival, and clinical features of the disease discussed and delineated. Some of the confusing elements of Ph 1 -positive ALL versus the BP of CML are also discussed and the two diseases put in perspective in light of the hypothesis of the pre-B cell (or its close lymphoid entities) origin of some of these leukemias.

Chromosome elimination in three Baltic, south Pacific and north-east Pacific hagfish species

We have confirmed that chromosome elimination occurs in the cells ofMyxine glutinosa, collected from the Baltic Sea off Sweden,Eptatretus cirrhatus from the south Pacific Ocean off the east coast of New Zealand, andE. stoutii from the north-east Pacific Ocean off Canada, similar to cells of four Japanese hagfish species. InM. Glutinosa, E. cirrhatus type A,E. cirrhatus type B andE. stoutii, the differences in chromosome number between spermatogonia (44, 72, 80 and 48) and somatic cells (28, 34, 34 and 34) were 16, 38, 46 and 14 respectively. The amount of DNA eliminated from presumptive somatic cells averaged 43.5%, 48.7%, 54.6% and 52.8% respectively. Euchromatic chromosomes and/or parts of chromosomes in addition to heterochromatic chromosomes were clearly eliminated inE. cirrhatus andE. stoutii. Adding our previous observations of four Japanese hagfish species, chromosome elimination occurs in all seven of the hagfish species. These results suggest that this phenomenon, chromosome elimination, generally occurs in the order Myxinida. In addition, B-chromosomes were observed in the germ cells ofE. cirrhatus andE. stoutii, similar to the cells ofE. okinoseanus, E. burgeri andParamyxine atami (E. atami). This fact suggests that B-chromosomes might exist generally in the family Eptatretidae.

A germline restricted, highly repetitive DNA sequence in Paramyxineatami: an interspecifically conserved, but somatically eliminated, element

Abstract In some species of hagfish, the phenomenon of chromosome elimination occurs during embryogenesis. However, only two repetitive DNA families are known to be represented in chromosomes that are eliminated from somatic cells of the Japanese hagfish Eptatretus okinoseanus. Using molecular analyses, another germ line-restricted, highly repetitive DNA family has been detected in another Japanese hagfish, Paramyxine atami. The repeat unit of this family, which is 83 bp long, has been designated “EEPa1”, for Eliminated Element of P. atami 1. DNA filter hybridization using EEPa1 as a probe revealed that this family is shared among several species and is conserved in the germline DNA. Although eliminated, repetitive DNA that is shared interspecifically has not been reported in hagfish species, cases of chromatin diminution and chromosome elimination processes have been described previously in other organisms.The patterns and intensities of hybridization signals suggest that members of the repetitive DNA family defined by EEPa1 have undergone concerted molecular evolution.