A role of the LIM-homeobox gene Lhx2 in the regulation of pituitary development

AbstractThe mammalian pituitary gland originates from two separate germinal tissues during embryonic development. The anterior and intermediate lobes of the pituitary are derived from Rathke's pouch, a pocket formed by an invagination of the oral ectoderm. The posterior lobe is derived from the infundibulum, which is formed by evagination of the neuroectoderm in the ventral diencephalon. Previous studies have shown that development of Rathke's pouch and the generation of distinct populations of hormone-producing endocrine cell lineages in the anterior/intermediate pituitary lobes is regulated by a number of transcription factors expressed in the pouch and by inductive signals from the ventral diencephalon/infundibulum. However, little is known about factors that regulate the development of the posterior pituitary lobe. In this study, we show that the LIM-homeobox gene Lhx2 is extensively expressed in the developing ventral diencephalon, including the infundibulum and the posterior lobe of the pituitary. Deletion of Lhx2 gene results in persistent cell proliferation, a complete failure of evagination of the neuroectoderm in the ventral diencephalon, and defects in the formation of the distinct morphological features of the infundibulum and the posterior pituitary lobe. Rathke's pouch is formed and endocrine cell lineages are generated in the anterior/intermediate pituitary lobes of the Lhx2 mutant. However, the shape and organization of the pouch and the anterior/intermediate pituitary lobes are severely altered due to the defects in development of the infundibulum and the posterior lobe. Our study thus reveals an essential role for Lhx2 in the regulation of posterior pituitary development and suggests a mechanism whereby development of the posterior lobe may affect the development of the anterior and intermediate lobes of the pituitary gland

Pruning random resistive memory for optimizing analogue AI

The rapid advancement of artificial intelligence (AI) has been marked by the large language models exhibiting human-like intelligence. However, these models also present unprecedented challenges to energy consumption and environmental sustainability. One promising solution is to revisit analogue computing, a technique that predates digital computing and exploits emerging analogue electronic devices, such as resistive memory, which features in-memory computing, high scalability, and nonvolatility. However, analogue computing still faces the same challenges as before: programming nonidealities and expensive programming due to the underlying devices physics. Here, we report a universal solution, software-hardware co-design using structural plasticity-inspired edge pruning to optimize the topology of a randomly weighted analogue resistive memory neural network. Software-wise, the topology of a randomly weighted neural network is optimized by pruning connections rather than precisely tuning resistive memory weights. Hardware-wise, we reveal the physical origin of the programming stochasticity using transmission electron microscopy, which is leveraged for large-scale and low-cost implementation of an overparameterized random neural network containing high-performance sub-networks. We implemented the co-design on a 40nm 256K resistive memory macro, observing 17.3% and 19.9% accuracy improvements in image and audio classification on FashionMNIST and Spoken digits datasets, as well as 9.8% (2%) improvement in PR (ROC) in image segmentation on DRIVE datasets, respectively. This is accompanied by 82.1%, 51.2%, and 99.8% improvement in energy efficiency thanks to analogue in-memory computing. By embracing the intrinsic stochasticity and in-memory computing, this work may solve the biggest obstacle of analogue computing systems and thus unleash their immense potential for next-generation AI hardware

A Unique Egg Cortical Granule Localization Motif Is Required for Ovastacin Sequestration to Prevent Premature ZP2 Cleavage and Ensure Female Fertility in Mice

<div><p>Monospermic fertilization is mediated by the extracellular zona pellucida composed of ZP1, ZP2 and ZP3. Sperm bind to the N-terminus of ZP2 which is cleaved after fertilization by ovastacin (encoded by <i>Astl</i>) exocytosed from egg cortical granules to prevent sperm binding. <i>Astl</i>^<i>Null</i> mice lack the post-fertilization block to sperm binding and the ability to rescue this phenotype with <i>Astl</i>^{<i>mCherry</i>} transgenic mice confirms the role of ovastacin in providing a definitive block to polyspermy. During oogenesis, endogenous ovastacin traffics through the endomembrane system prior to storage in peripherally located cortical granules. Deletion mutants of ovastacin^mCherry expressed in growing oocytes define a unique 7 amino acid motif near its N-terminus that is necessary and sufficient for cortical granule localization. Deletion of the 7 amino acids by CRISPR/Cas9 at the endogenous locus (<i>Astl</i>^<i>Δ</i>) prevents cortical granule localization of ovastacin. The misdirected enzyme is present within the endomembrane system and ZP2 is prematurely cleaved. Sperm bind poorly to the zona pellucida of <i>Astl</i>^<i>Δ/Δ</i> mice with partially cleaved ZP2 and female mice are sub-fertile.</p></div

Ldb1 is essential for development of Nkx2.1 lineage derived GABAergic and cholinergic neurons in the telencephalon

The progenitor zones of the embryonic mouse ventral telencephalon give rise to GABAergic and cholinergic neurons. We have shown previously that two LIM-homeodomain (LIM-HD) transcription factors, Lhx6 and Lhx8, that are downstream of Nkx2.1, are critical for the development of telencephalic GABAergic and cholinergic neurons. Here we investigate the role of Ldb1, a nuclear protein that binds directly to all LIM-HD factors, in the development of these ventral telencephalon derived neurons. We show that Ldb1 is expressed in the Nkx2.1 cell lineage during embryonic development and in mature neurons. Conditional deletion of Ldb1 causes defects in the expression of a series of genes in the ventral telencephalon and severe impairment in the tangential migration of cortical interneurons from the ventral telencephalon. Similar to the phenotypes observed in Lhx6 or Lhx8 mutant mice, the Ldb1 conditional mutants show a reduction in the number of both GABAergic and cholinergic neurons in the telencephalon. Furthermore, our analysis reveals defects in the development of the parvalbumin-positive neurons in the globus pallidus and striatum of the Ldb1 mutants. These results provide evidence that Ldb1 plays an essential role as a transcription co-regulator of Lhx6 and Lhx8 in the control of mammalian telencephalon development

In-memory and in-sensor reservoir computing with memristive devices

Despite the significant progress made in deep learning on digital computers, their energy consumption and computational speed still fall short of meeting the standards for brain-like computing. To address these limitations, reservoir computing (RC) has been gaining increasing attention across communities of electronic devices, computing systems, and machine learning, notably with its in-memory or in-sensor implementation on the hardware–software co-design. Hardware regarded, in-memory or in-sensor computers leverage emerging electronic and optoelectronic devices for data processing right where the data are stored or sensed. This technology dramatically reduces the energy consumption from frequent data transfers between sensing, storage, and computational units. Software regarded, RC enables real-time edge learning thanks to its brain-inspired dynamic system with massive training complexity reduction. From this perspective, we survey recent advancements in in-memory/in-sensor RC, including algorithm designs, material and device development, and downstream applications in classification and regression problems, and discuss challenges and opportunities ahead in this emerging field

Ovastacin cortical granule localization motif.

<p><b>(a)</b> Growing oocytes (60–65 μm) were injected with cRNA encoding an ovastacin^mCherry fusion protein (top) with a signal peptide (1–23 aa), a pro segment (24–85 aa) and the mature ovastacin enzyme (86–435 aa) containing an active site (asterisk, ¹⁸²<u><b>HE</b></u>LM<u><b>H</b></u>VLGFW<u><b>H</b></u>¹⁹²) fused to mCherry (236 aa). Six hr after injection, oocytes were fixed, permeabilized and stained with antibodies to ovastacin, LCA-FITC and Hoechst and imaged by confocal and DIC microscopy (bottom). Scale bar, 20 μm. <b>(b)</b> Same as <b>(a)</b> after injection of cRNA encoding either ovastacin 1–89 aa or ovastacin 1–23; 82–435 aa indicated in <b>(e)</b>. <b>(c)</b> Same as <b>(a)</b> after injection of cRNA encoding either ovastacin 1–64 aa or ovastacin 1–23; 61–435 aa indicated in <b>(e)</b>. <b>(d)</b> Same as <b>(a)</b> after injection of cRNA encoding either ovastacin 1–51 aa or ovastacin 1–28; 52–64 aa indicated in <b>(e)</b>. <b>(e)</b> Schematic representation of three pairs of complementary deletion constructs of ovastacin^mCherry fusion proteins injected into growing oocytes. Dotted lines indicate the minimal sequence (ovastacin^Δ52–64) for localization of the fusion protein to cortical granules. <b>(f)</b> Primary amino acid sequences of ovastacin from 10 mammals were aligned to mouse ovastacin^47-69. The conservation of mouse ovastacin^Δ52–64 cortical granule localization signal is indicated by asterisks. <b>(g)</b> Same as <b>(a)</b> after injection of cRNA encoding ovastacin 1–28; 52–58.</p

Ovastacin is not present in cortical granules after partial deletion of the localization motif.

<p><b>(a)</b> Schematic representation of the CRISPR/Cas9 deletion mutation in <i>Astl</i> exon 2 that encodes ovastacin^Δ52–58. <b>(b)</b> Wild-type GV-intact oocytes were fixed, permeabilized and stained with antibodies to ovastacin, LCA-FITC and imaged by confocal and DIC microscopy. <b>(c)</b> Same as <b>(b)</b> with GV-intact oocytes, ovulated MII eggs, 1-cell zygotes and 2-cell embryos from <i>Astl</i>^<i>Δ/Δ</i> mice. <b>(d)</b> Same as <b>(b)</b> with GV-intact oocytes and ovulated MII eggs from <i>Astl</i>^<i>+/Δ</i> mice. <b>(e)</b> GV-intact oocytes and ovulated MII eggs from <i>Astl</i>^<i>+/+</i>; <i>Astl</i>^{<i>mCherry</i>} and <i>Astl</i>^<i>+/Δ</i>; <i>Astl</i> ^{<i>mCherry</i>} mice were fixed, permeabilized and imaged by confocal and DIC microscopy. Scale bars, 20 μm.</p

Premature cleavage of ZP2 affects fertility of <i>Astl</i> mutant mice.

<p><b>(a)</b> Immunoblot of zonae pellucidae from wild-type (Ctrl), <i>Astl</i>^<i>+/Δ</i> and <i>Astl</i>^<i>Δ/Δ</i> ovulated eggs as well as wild-type 2C embryos (Ctrl) stained with a monoclonal antibody (M2c.2) that binds to the C-terminus of ZP2 and detected intact (upper arrow) and cleaved (lower arrow) protein. Molecular mass (kD) on left. <b>(b)</b> Sperm binding to wild-type eggs, 2C embryos, <i>Astl</i>^<i>+/Δ</i> and <i>Astl</i>^<i>Δ/Δ</i> eggs. Confocal projections (upper) and DIC (lower) images were obtained after fixation and staining nuclei with Hoechst. Arrows, nuclei; PB, polar body. Scale bar, 20 μm. <b>(c)</b> Average (± s.e.m) number of sperm bound to wild-type eggs (Ctrl), 2C embryos (Ctrl), <i>Astl</i>^<i>+/Δ</i> and <i>Astl</i>^<i>Δ/Δ</i> eggs imaged in <b>(b)</b>. N = 30 in each case. <b>(d)</b> <i>In vitro</i> fertilization with wild-type (left), <i>Astl</i>^<i>+/Δ</i> (center) and <i>Astl</i>^<i>Δ/Δ</i> (right) eggs with and without zonae pellucidae. Fertilization was determined by the presence of 2 pronuclei 12 hr after insemination. <b>(e)</b> Dot density (left) and associated box plots (right) of litters from wild-type (Control), <i>Astl</i>^<i>+/Δ</i> and <i>Astl</i>^<i>Δ/Δ</i> females co-caged with fertile male mice. The box includes the mean (horizontal line) and data between the 25^th and 75^th percentile. Error bars indicate the 90^th and 10^th percentiles and outliers are indicated by dots. Statistical differences in <b>c</b> and <b>d</b> were determined by 2-tailed Student’s T-test, P <0.001.</p