Reduction of genetic diversity in 'Alala (Hawaiian crow; Corvus hawaiiensis) between the late 1800s and the late 1900s.

Genetic and genomic data are increasingly used to aid conservation management of endangered species by providing insights into evolutionary histories, factors associated with extinction risks, and potential for future adaptation. For the 'Alala, or Hawaiian crow (Corvus hawaiiensis), genetic concerns include negative correlations between inbreeding and hatching success. However, it is unclear if low genetic diversity and inbreeding depression are consequences of a historical population bottleneck, or if 'Alala had historically low genetic diversity that predated human influence, perhaps as a result of earlier declines or founding events. In this study, we applied a hybridization-based sequence capture to generate a genome-wide single nucleotide polymorphism (SNP) dataset for comparing historical specimens collected in the 1890s, when 'Alala were more numerous, to samples taken between 1973 and 1998, when 'Alala population densities were near the lowest documented levels in the wild, prior to all individuals being collected for captive rearing. We found low genome-wide diversity in both sample groups, however, the modern sample group (1973 to 1998 cohort) exhibited relatively fewer polymorphic alleles, a lower proportion of polymorphic loci, and lower observed heterozygosity, consistent with a population decline and potential bottleneck effects. These results combined with a current low population size highlight the importance of continued efforts by conservation managers to mitigate inbreeding and maintain founder representation to preserve what genetic diversity remains.

Genetically-biased fertilization in APOBEC1 complementation factor (A1cf) mutant mice.

Meiosis, recombination, and gametogenesis normally ensure that gametes combine randomly. But in exceptional cases, fertilization depends on the genetics of gametes from both females and males. A key question is whether their non-random union results from factors intrinsic to oocytes and sperm, or from their interactions with conditions in the reproductive tracts. To address this question, we used in vitro fertilization (IVF) with a mutant and wild-type allele of the A1cf (APOBEC1 complementation factor) gene in mice that are otherwise genetically identical. We observed strong distortion in favor of mutant heterozygotes showing that bias depends on the genetics of oocyte and sperm, and that any environmental input is modest. To search for the potential mechanism of the 'biased fertilization', we analyzed the existing transcriptome data and demonstrated that localization of A1cf transcripts and its candidate mRNA targets is restricted to the spermatids in which they originate, and that these transcripts are enriched for functions related to meiosis, fertilization, RNA stability, translation, and mitochondria. We propose that failure to sequester mRNA targets in A1cf mutant heterozygotes leads to functional differences among spermatids, thereby providing an opportunity for selection among haploid gametes. The study adds to the understanding of the gamete interaction at fertilization. Discovery that bias is evident with IVF provides a new venue for future explorations of preference among genetically distinct gametes at fertilization for A1cf and other genes that display significant departure of Mendelian inheritance.

Loss of mouse Y chromosome gene Zfy1 and Zfy2 leads to spermatogenesis impairment, sperm defects, and infertility.

Using mice with Y chromosome deficiencies and supplementing Zfy transgenes, we, and others, have previously shown that the loss of Y chromosome Zfy1 and Zfy2 genes is associated with infertility and spermiogenic defects and that the addition of Zfy transgenes rescues these defects. In these past studies, the absence of Zfy was linked to the loss of other Y chromosome genes, which might have contributed to spermiogenic phenotypes. Here, we used CRISPR/Cas9 to specifically remove open reading frame of Zfy1, Zfy2, or both Zfy1 and Zfy2, and generated Zfy knockout (KO) and double knockout (DKO) mice. Zfy1 KO and Zfy2 KO mice were both fertile, but the latter had decreased litters size and sperm number, and sperm headshape abnormalities. Zfy DKO males were infertile and displayed severe spermatogenesis defects. Postmeiotic arrest largely prevented production of sperm and the few sperm that were produced all displayed gross headshape abnormalities and structural defects within head and tail. Infertility of Zfy DKO mice could be overcome by injection of spermatids or sperm directly to oocytes, and the resulting male offspring had the same spermiogenic phenotype as their fathers. The study is the first describing detailed phenotypic characterization of mice with the complete Zfy gene loss. It provides evidence supporting that the presence of at least one Zfy homolog is essential for male fertility and development of normal sperm functional in unassisted fertilization. The data also show that while the loss of Zfy1 is benign, the loss of Zfy2 is mildly detrimental for spermatogenesis.

Does Low PAPP-A Predict Adverse Placenta-Mediated Outcomes in a Low-Risk Nulliparous Population? the Great Obstetrical Syndromes (GOS) Study.

OBJECTIVE: First-trimester low concentration of pregnancy-associated plasma protein A (PAPP-A) has been associated with adverse perinatal outcomes in high-risk populations. This study aimed to estimate the ability of PAPP-A to identify adverse outcomes in a low-risk population. METHODS: The study investigators recruited nulliparous women with singleton pregnancy at their 11-13-week ultrasound scan. Serum samples were collected, and maternal PAPP-A concentration was measured using the B⋅R⋅A⋅H⋅M⋅S PAPP-A KRYPTOR (ThermoFisher Scientific, Hennigsdorf, Germany) automated assay. PAPP-A was reported in multiple of median (MoM) adjusted for GA. Participants were followed until delivery for pregnancy outcomes including preeclampsia (PE), SGA <3rd percentile, and fetal death. Receiver operating characteristic curves with the area under the curve (AUC) were used to evaluate the predictive value of PAPP-A. The investigators calculated the detection rates (DRs) and positive predictive values (PPVs) of a PAPP-A < 0.4 MoM. RESULTS: The study investigators recruited 4739 eligible participants at a mean GA of 13 ± 6 weeks. The investigators observed 232 (4.9%) cases of PE, 84 (1.8%) cases of SGA, and 14 (0.3%) fetal deaths. PAPP-A was moderately associated with PE (AUC 0.57; 95% CI 0.53-0.61) and SGA (AUC 0.62; 95% CI 0.56-0.69), but not with fetal death (AUC 0.43; 95% CI 0.23-0.63). PAPP-A < 0.4 MoM was observed in 364 (7.7%) participants and had poor predictive values for PE (DR 9.8%; PPV 6.3%), SGA (DR 18.1%; PPV 4.4%), and fetal death (DR 21.4%; PPV 0.9%). CONCLUSION: Isolated first trimester PAPP-A has a limited predictive value for adverse pregnancy outcomes (other than trisomies). Low PAPP-A (<0.4 MoM) should be used in combination with other markers for the prediction of PE, SGA, or fetal death, and it does not constitute an indication for low-dose aspirin.