The haploid syndrome in isogenic haploid frog embryos of Rana pipiens derived by nuclear transplantation

Abstract

The majority of haploid frogs are non-viable and few survive past early larval stages. While animals vary with respect to specific abnormalities, they succumb to the variety of defects which collectively comprise the haploid syndrome. This poor viability has been ascribed to unmasked lethal and semi-lethal genes or to alterations in the nucleocytoplasmic ratio. This investigation was designed to test these hypotheses by determining the uniformity of anomalies in clones of isogenic haploid embryos.Animal hemisphere nuclei of stage 10 androgenetic haploids of Rana pipiens were transpIanted into activated and enucleated eggs of uniform size. Haploid embryos were selected from eggs whose cleavage times coincided with those of the fertilized controls. Genetically identical haploid embryos displayed differences i n the variety as well as the severity of abnormalities. Thus, specific lethal genes are not responsible for the variability in defects seen in the haploid syndrome. We ascribe haploid inviability and variations within isogenic clones to a lack of heterozygosity of the haploid nucleus with resultant inability of the haploid nucleus to function in a heterogeneous environment, i.e., the egg cytoplasm.During embryonic development of haploid frog embryos, the majority of the organisms are non-viable. Few haploids survive past early larval stages. Cleavage of haploid embryos occurs at a normal rate; thereafter, development is characterized by delayed differentiation and stunted growth. As development progresses a variety of defects arise in several organs. These defects have been described in detail (Porter, '39; Briggs, '49; Miyada, '60; Volpe and Dasgupta, '62) for androgenetic and gynogenetic haploids. Briefly, the abnormalities are in the form of shortened neural plates, changes in body proportions, microcephalic heads, edematous abdomens, and poorly developed circulatory systems. While abnormalities vary from embryo to embryo in a group of haploids, both in their nature and degree of severity, collectively these deficiencies are referred to as the haploid syndrome. The syndrome is essentially similar in androgenetic and gynogenetic haploids.Hertwig ('13) proposed altered nucleocytoplasmic ratio as being responsible for the poor viability of haploid embryos.Briggs ('49) the development of androgenetic haploids produced from large and small eggs of R a n a pipiens. Haploids which developed from smaller eggs lived longer and exhibited deficiencies to a less severe extent. Subtelny ('58) rigorously tested Hertwig's 19 13 proposal by transplanting haploid nuclei into activated and enucleated eggs of Rana pipiens. Some of these eggs cleaved later than fertilized controls. These embryos were demonstrated to be diploids. It was reasoned that the haploid nucleus divided once while the cytoplasm failed to do so. Thus, these embryos were considered to be homozygous diploids whose nucleo-cytoplasmic ratio was not altered. Subtelny's rationale was that if these homozygous diploids survived, then haploid deaths cou...

The Production of Parthenogenetic Mammalian Embryos and Their Use in Biological Research

“…It is extremely rare for haploid amphibians to develop into adults (e.g. Dasgupta & Matsumoto, 1972) and only a few cases have been recorded (Miyada, 1960). However, if diploids are formed by suppression of the 2PB then many develop to maturity; in the best cases about one third of the blastulae have formed adults (Volpe, 1970).…”

Haploidy-linked cell proliferation defects limit larval growth in Zebrafish

“…Moreover, fish or amphibian haploid embryos develop until the late larval stages without drastic changes in the ploidy state, indicating that haploidy is stable in these species compared to mammals (11)(12)(13)(14). However, despite the lack of the detrimental features of imprinting misregulation and haploid instability, non-mammalian vertebrate haploid embryos manifest severe morphological defects with poor growth of organs such as the brain and eyes and succumb to lethality after hatching (12,(14)(15)(16)(17)(18). Forced diploidization of these haploid embryos by artificial induction of whole-genome duplication in the early cleavage stages resolves these developmental defects, suggesting that the haploid state per se, rather than loss of heterozygosity of deleterious recessive alleles, causes these defects (13,(19)(20)(21).…”

“…In the complex profile of haploid syndrome, a particularly common abnormality across non-mammalian vertebrate species is severe growth retardation of organs, such as the brain and eyes (Dasgupta and Matsumoto, 1972; Fankhauser and Griffiths, 1939; Hertwig, 1911; Oppermann, 1913; Purdom, 1969; Uwa, 1965). Forced diploidization of haploid larvae by artificial induction of whole-genome duplication in the early cleavage stages resolves organ retardations, suggesting that the haploid state per se, rather than loss of heterozygosity of deleterious recessive alleles, causes these defects (Menon and Nair, 2018; Nagy et al, 1978; Streisinger et al, 1981; Subtelny, 1958).…”

Gynogenetic diploids, tetraploids, or octoploids, and a path to polyploidy in anuran amphibians

“…Several investigations have tested early hypotheses that there is an altered relationship between the nuclear and cytoplasmic material (Hertwig 1913), or that the haploid syndrome results from unmasking lethal genes (Darlington 1937). Dasgupta and Matsumoto (1972) rejected the lethal genes hypothesis, which produced isogenic gynogenetic and androgenetic haploid clones of R. pipiens. Genetically identical haploid embryos had developmental variability comparable to that observed in non-isogenic haploid siblings.…”