Biology subjects

Li, P. P.

Publications and source records attributed to Li, P. P..

5 recordsLinked to original sources

bioRxiv2026

Optimizing the efficiency of assisted reproduction procedures in the common marmoset (Callithrix jacchus) improved IVF outcomes

The marmoset has emerged as a model species for genetic studies of complex neurodevelopmental conditions because of their brain development, behavior, communication, and compact size. IVF has been used to generate wild-type and transgenic marmoset embryos, but inefficiency of IVF in the marmoset compared to other primates poses challenges for genetic manipulation. To address this limitation, we analyzed the association between variables of age, number of cycles, and progesterone levels for IVF and embryology outcomes. Longitudinal data collected over 2 years indicated that the progesterone levels 24 hours after Cloprostenol sodium (Estrumate) administration, the number of days of ovarian stimulation during an IVF cycle, and the number of oocyte retrievals that an animal had undergone all influenced IVF cycle outcomes. Higher serum progesterone levels at cycle start were negatively correlated with the likelihood of fertilized eggs progressing to the cleavage stage of embryo development. Additionally, a shorter duration of ovarian stimulation (ranging 7 to 14 days of medication) coupled with a GnRH antagonist correlated with an increased percentage of fertilized eggs. We observed a trend that a shorter hormonal stimulation cycle length was associated with a higher percentage of embryos reaching the cleavage stage. The optimization of stimulation cycle protocol and embryology has led to a high percentage of implantation after embryo transfer regardless of whether the embryo was fresh or cryopreserved. These findings suggest that shorter IVF cycles and a progesterone level <10 ng/mL at cycle start were correlated with an increased likelihood of a cleavage stage embryo development.

developmental biology↗

bioRxiv2026

Analysis of sperm processing and cryopreservation procedures in the common marmoset (Callithrix jacchus) to reduce fragmentation and maximize total and progressive motility

The marmoset has emerged as an ideal species for studying complex neurodevelopmental diseases, and IVF is required for gene-editing success. Reliable sperm processing is paramount to several IVF techniques, including traditional insemination. If not used immediately, thermal stress from cryopreservation diminishes sperm quality, requiring improved processing methods. Swim-up and gradient methods may limit adequate sperm quality, and the lack of a standardized freezing protocol often results in impaired post-thaw motility. Thus, reliable standards for sperm processing and cryopreservation in the marmoset are needed to support vital IVF processes. Collected semen underwent one of four pre-processing incubation steps before processing by swim-up, sucrose gradient, or a microfluidics assay. Sperm parameters were assessed using a Hamilton Thorne Computer Assisted Sperm Analysis (CASA) system. To evaluate cryopreservation, microfluidics-processed sperm were subjected to five protocols using different cryoprotectants and cooling methods. After thawing, sperm samples were analyzed with the CASA system and a DNA fragmentation assay. Incubation for 30 minutes at 38C in TYH media decreased sperm aggregation, and subsequent microfluidics resulted in a higher percentage of motile and progressively motile sperm than swim-up or gradient methods. Our optimized cryopreservation protocol consistently achieved at least 20% progressive motility, a key benchmark for usable marmoset sperm, while previously published or commercial methods were less consistent. The cryopreservation protocol outperformed other published methods, having the least significant change in post-thaw motility without causing DNA damage. These findings establish standardized methods for reliably procuring and storing sperm samples for IVF or husbandry in the common marmoset.

developmental biology↗

bioRxiv2026

A bipolar disorder-associated ultra-rare AKAP11 protein-truncating variant attenuates stimulus-dependent PKA activation and induces anxiety- and depression-related behaviors in mice

Rare genetic variants associated with psychiatric disorders are thought to have larger individual effect sizes and direct biological roles, offering a unique opportunity for understanding causal relationships between genetic architecture and disease phenotypes. A recent whole-exome sequencing meta-analysis identified an increased burden of ultra-rare protein-truncating variants (PTVs) in AKAP11 in patients with bipolar disorder and schizophrenia. AKAP11 encodes an A-kinase anchoring protein that mediates the association of protein kinase A (PKA) and its substrates. How ultra-rare AKAP11 variants contribute to psychiatric disorder pathogenesis remains unknown. Here, using CRISPR-Cas9 genome editing, we introduced into the mouse Akap11 locus an ultra-rare PTV identified in a human patient with bipolar disorder. This ultra-rare PTV reduced Akap11 mRNA and protein levels without producing stable novel mRNA isoforms, leading to Akap11 haploinsufficiency. Male heterozygous mice exhibited behavioral abnormalities consistent with anxiety- and depression-like phenotypes. Transcriptomic and proteomic profiling of the neocortex revealed molecular changes involving synaptic organization, synaptic signaling, and neurite morphogenesis. Notably, the heterozygous mutant showed selective elevation in type I, but not type II, PKA regulatory subunits, as well as PKA catalytic subunits, in the neocortex. Functionally, these changes were accompanied by reduced phosphorylation of PKA substrates, attenuated stimulus-dependent PKA activity in cortical excitatory neurons, and impaired nascent dendritic development in cortical neurons. Together, our study presents a clinically relevant and genetically precise mouse model that provides mechanistic insight into how ultra-rare PTVs may contribute to psychiatric disorder pathogenesis, and a platform for testing rational therapeutics.

neuroscience↗

bioRxiv2023

Bidirectional transcription at the PPP2R2B gene locus in spinocerebellar ataxia type 12

OBJECTIVESpinocerebellar ataxia type 12 (SCA12) is a neurodegenerative disease caused by expansion of a CAG repeat in the PPP2R2B gene. Here we tested the hypothesis that the PPP2R2B antisense (PPP2R2B-AS1) transcript containing a CUG repeat is expressed and contributes to SCA12 pathogenesis. METHODSExpression of PPP2R2B-AS1 transcript was detected in SCA12 human induced pluripotent stem cells (iPSCs), iPSC-derived NGN2 neurons, and SCA12 knock-in mouse brains using strand-specific RT-PCR (SS-RT-PCR). The tendency of expanded PPP2R2B-AS1 (expPPP2R2B-AS1) RNA to form foci, a marker of toxic processes involving mutant RNAs, was examined in SCA12 cell models by fluorescence in situ hybridization. The toxic effect of expPPP2R2B-AS1 transcripts on SK-N-MC neuroblastoma cells was evaluated by caspase 3/7 activity. Western blot was used to examine the expression of repeat associated non-ATG-initiated (RAN) translation of expPPP2R2B-AS1 transcript in SK-N-MC cells. RESULTSThe repeat region in PPP2R2B gene locus is bidirectionally transcribed in SCA12 iPSCs, iPSC-derived NGN2 neurons, and SCA12 mouse brains. Transfected expPPP2R2B-AS1 transcripts are toxic to SK-N-MC cells, and the toxicity may be mediated, at least in part, by the RNA secondary structure. The expPPP2R2B-AS1 transcripts form CUG RNA foci in SK-N-MC cells. expPPP2R2B-AS1 transcript is translated in the Alanine ORF via repeat-associated non-ATG (RAN) translation, which is diminished by single nucleotide interruptions within the CUG repeat, and MBNL1 overexpression. INTERPRETATIONThese findings suggest that PPP2R2B-AS1 contributes to SCA12 pathogenesis, and may therefore provide a novel therapeutic target for the disease.

neuroscience↗

bioRxiv2021

RNA toxicity and perturbation of rRNA processing in spinocerebellar ataxia type 2

BACKGROUNDSpinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disease caused by expansion of a CAG repeat in Ataxin-2 (ATXN2) gene. The mutant ATXN2 protein with a polyglutamine tract is known to be toxic and contributes to the SCA2 pathogenesis. OBJECTIVEHere we tested the hypothesis that the mutant ATXN2 transcript with an expanded CAG repeat (expATXN2) is also toxic and contributes to SCA2 pathogenesis. METHODSThe toxic effect of expATXN2 transcripts on SK-N-MC neuroblastoma cells and primary mouse cortical neurons was evaluated by caspase 3/7 activity and nuclear condensation assay, respectively. RNA immunoprecipitation assay was performed to identify RNA binding proteins (RBPs) that bind to expATXN2 RNA. Quantitative PCR was used to examine if rRNA processing is disrupted in SCA2 and Huntington disease (HD) human brain tissue. RESULTSexpATXN2 RNA induces neuronal cell death, and aberrantly interacts with RBPs involved in RNA metabolism. One of the RBPs, transducin {beta}-like protein 3 (TBL3), involved in rRNA processing, binds to both expATXN2 and expanded huntingtin (expHTT) RNA in vitro. rRNA processing is disrupted in both SCA2 and HD human brain tissue. CONCLUSIONThese findings provide the first evidence of a contributory role of expATXN2 transcripts in SCA2 pathogenesis, and further support the role expHTT transcripts in HD pathogenesis. The disruption of rRNA processing, mediated by aberrant interaction of RBPs with expATXN2 and expHTT transcripts, suggest a point of convergence in the pathogeneses of repeat expansion diseases with potential therapeutic implications.

neuroscience↗