Low intracellular pH is involved in the early embryonic death of DDK mouse eggs fertilized by alien sperm

Abstract

Intracellular pH was measured in normal 8-cell stage mouse embryos and in embryos from a cross between DDK females and C3H males. DDWC3H embryos display the DDK syndrome and spontaneously begin to decompact toward the late 16-cell stage. Ultimately, 90% fail to form blastocysts. Normal embryos have a resting intracellular pH close to neutrality. In DDKIC3H embryos a substantial proportion (46%) has an intracellular pH below 6.7. An equivalent proportion of DDK/C3H embryos was found previously to show slow communication through gap junctions at the 8-cell stage. This is probably a consequence of low intracellular pH. In normal embryos the weak acid, butyric acid, decreased intracellular pH and slowed the transfer of Lucifer Yellow through gap junctions. Normal embryos treated with butyrate for between 1 and 6 hr beginning at the 8-cell stage and cultured for 24 hr, reproduced the DDWC3H phenotype. After 48 hr some butyrate treated embryos recovered, while others remained as decompacted morulae. Treatment of control and DDWC3H 8-cell stage embryos with dibutyryl cyclic AMP or forskolin, which will increase intracellular cyclic AMP, speeded gap junctional communication. Forskolin treatment prevented expression of the DDK syndrome in DDWC3H embryos, although the rescue was transient and the syndrome returned when forskolin was removed. The finding that the DDK syndrome is manifested as low intracellular pH may provide clues to the molecular basis of the defect. o 1994 Wiley-Liss, Inc.

The Paternal Gene of the DDK Syndrome Maps to the Schlafen Gene Cluster on Mouse Chromosome 11

“…Although the presence of scattered ancestral variants is not surprising, per se, it is rare to find large numbers of ancestral variants that consistently contradict the expected phylogeny spanning extensive regions because normally recombination would erase the linkage disequilibrium between them. Rearrangements may suppress recombination and, therefore, in this situation sequence homology is dependent on the presence or Buehr et al (1987); Leclerc et al (1994); this study KK The table provides the strain name, phylogenetic origin of the haplotype in the candidate interval for the paternal gene defined by progeny testing and whether the allele at the paternal gene is incompatible (I) or compatible (C) with the maternal DDK factor. In addition, the table provides the allele present in each strain at each of the 12 SNPs with the highest level of association with the DDK syndrome phenotype.…”

“…All of these strains, with the exception of DDK, carry an incompatible allele at the paternal gene (Wakasugi et al 1967;Wakasugi 1973Wakasugi , 1974Wakasugi and Morita 1977;Mann 1986;Buehr et al 1987;Baldacci et al 1992Baldacci et al , 1996Sapienza et al 1992;Leclerc et al 1994;Pardo-Manuel de Villena et al 1996, 1997, 1999, suggesting that the DDK strain carries rare mutations in both maternal and paternal components of the syndrome. Recently this view has been challenged by a report by Zhao et al (2002) demonstrating that the alleles present at the paternal gene in two wild-derived inbred strains, MOM (Mus musculus molossinus) and CASP (Mus musculus castaneus) are fully compatible with the DDK maternal factor.…”

Biological pH buffers in IVF: help or hindrance to success

“…Detailed studies on embryo metabolism, examination of tubal fluid composition and other physiologic, molecular and biochemical insights have led to improved modifications of media formulations. This has resulted in several excellent culture media, both mono and sequential systems, giving laboratories multiple choices in terms of selection of ingredients such as glucose concentration or amino acid complement [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, despite the number of options in regard to substrate selection for embryo culture media for use within the laboratory incubator, the ability to select from a variety of pH buffers in handling media for use outside the incubator is extremely limited.…”

“…External pH of culture media (pHe) influences sperm binding and motility [7][8][9], oocyte maturation [10,11] and embryo development [12][13][14][15][16], though confounding factors such as bicarbonate and CO 2 levels exist. Improper intracellular pH (pHi) can impede sperm function [19][20][21][22].…”

“…Improper intracellular pH (pHi) can impede sperm function [19][20][21][22]. Improper pHi is also detrimental to embryo development [23][24][25][26][27], impairs embryo metabolism [28,29], alters organelle localization [30], and even retards resulting fetal growth [31]. Furthermore, periodic fluctuations in environmental conditions, such as the pHe of media, can be harmful as these can be transduced into deleterious intracellular perturbations [32].…”