Altered Protamine 2 Expression Is Uncommon In Donors of Known Fertility, but Common Among Men With Poor Fertilizing Capacity, and May Reflect Other Abnormalities of Spermiogenesis

Abstract

During the spermatid elongation stage of spermiogenesis approximately 85% of sperm nuclear histones are replaced by protamines. Protamines increase the packing ratio of sperm chromatin, presumably facilitating sperm motility and function. In this study we evaluated the incidence of abnormal protamine expression in 75 patients undergoing in vitro fertilization (IVF) and 50 donors of known fertility by isolation of sperm nuclear proteins, quantitative gel electrophoresis, and Western blot analysis. In addition, we evaluated the relationship between abnormal protamine expression and semen quality, sperm penetration ability, chromatin stability, and IVF outcome. Seventeen percent (13/75) of IVF patients had no measurable protamine 2 (P2) versus 0% (0/50) of donors of known fertility (P < .005). Sperm penetration rates were decreased in 12 of 13 patients without P2, and mean penetration rates (4.6 ± 1.2 vs 32.8 ± 2.9, P < .005), normal morphology (22.4 ± 3.6 vs 48.7 ± 4.2, P < .05), and progressive motility (22.3 ± 2.5 vs 35.4 ± 2.1, P < .05) were all significantly decreased compared with patients with measurable P2. The mean sperm concentration was not significantly different. The presence of protamine precursor bands was also associated with a diminished penetration capacity (18.4 ± 2.8 vs 36.7 ± 3.0, P < .05). Sperm chromatin decondensation following exposure to heparin sulfate was significantly increased in patients without a measurable P2 band. Twelve patients with no measurable P2 underwent intracytoplasmic sperm injection (ICSI), with 6 patients (6/12, 50%) becoming pregnant. ICSI fertilization and subsequent embryo cleavage were not different in patients without P2 compared with other patients undergoing ICSI. These data indicate that abnormal sperm protamine levels are a common defect in infertility patients, but not in donors of known fertility. It appears that abnormal protamine levels may reflect defects of late spermiogenesis, including sperm penetration capacity.

Differential sperm histone retention in normozoospermic ejaculates of infertile men negatively affects sperm functional competence and embryo quality

“…It has been shown that an altered histone‐to‐protamine ratio, or more specifically, increased histone retention in sperm chromatin affects male fertility by decreasing sperm concentration, and motility, increasing DNA damage and poor embryo outcome 22,23,26,32,52 . We observed a positive association between histone H3 and spermatozoa with high DNA damage.…”

Determinación de la calidad seminal, daño al DNA espermático y su relación en la fecundación y desarrollo embrionario (día 2) en pacientes con problemas reproductivos

“…La cromatina pasa por un proceso de compactación (Kim, 2018;Wang, et al, 2019), siendo un evento que empieza en el proceso de espermiogénesis (Jodar & Olivia, 2014), empezando en la fase acrosómica, donde la topoisomerasa II cumple el papel de desenrollar las cadenas del DNA y por medio de la hiperacetilación de las histonas, así como otras modificaciones, se disocian los nucleosomas (Carrell, et al, 2007). Se incorporan variantes de histona testículo-específicas e histonas modificadas post-traduccionalmente (PTMs) (Carrell & Liu, 2001). Posteriormente, las proteínas de transición nuclear (Transition nuclear protein TNP) 1 y 2 (Akmal, et al, 2016;Brewer, et al, 2002) se unen al DNA temporalmente para después ser reemplazadas por protaminas (Jodar & Olivia, 2014; Torres-Flores & Hernández-Hernández, 2020).…”

“…Se pueden encontrar dos tipos de protaminas (P), P1 y la familia de P2 se conforma de P2, P3 y P4 (Oliva, 2006). Se reporta la presencia de la P1 en todos los mamíferos y se compone de 50 aminoácidos, mientras que P2 pasa por un proceso de condensación, al principio se conforma de 103 aminoácidos y se corta a 53 al unirse a una proteína precursora del DNA (no está presente en los esperamtozoides del toro ni del jabalí) (Carrell & Liu, 2001). El espermatozoide madura en el epidídimo, es aquí donde a través de enlaces disulfuro (cisteína) se estabilizan los complejos de protaminas que mantendran al DNA compactado (Oliva, 2006;Yoshida, et al, 2018), los cambios significativos a la cromatina se resumen en la Figura 3.…”