Aptasensor for Quantification of Leptin Through PCR Amplification of Short DNA-Aptamers

Protein quantification is traditionally performed through enzyme-linked immunosorbent assay (ELISA), which involves long preparation times. To overcome this, new approaches use aptamers as an alternative to antibodies. In this paper, we present a new approach to quantify proteins with short DNA aptamers through polymerase chain reaction (PCR) resulting in shorter protocol times with comparatively improved limits of detection. The proposed method includes a novel way to quantify both the target protein and the corresponding short DNA-aptamers simultaneously, which also allows us to fully characterize the performance of aptasensors. Human leptin is used as a target protein to validate this technique, because it is considered an important biomarker for obesity-related studies. In our experiments, we achieved the lowest limit of detection of 100 pg/mL within less than 2 h, a limit affected by the dissociation constant of the leptin aptamer, which could be improved by selecting a more specific aptamer. Because of the simple and inexpensive approach, this technique can be employed for Lab-On-Chip implementations and for rapid "on-site" quantification of proteins.

Atlas of Circadian Metabolism Reveals System-wide Coordination and Communication between Clocks

Metabolic diseases are often characterized by circadian misalignment in different tissues, yet how altered coordination and communication among tissue clocks relate to specific pathogenic mechanisms remains largely unknown. Applying an integrated systems biology approach, we performed 24-hr metabolomics profiling of eight mouse tissues simultaneously. We present a temporal and spatial atlas of circadian metabolism in the context of systemic energy balance and under chronic nutrient stress (high-fat diet [HFD]). Comparative analysis reveals how the repertoires of tissue metabolism are linked and gated to specific temporal windows and how this highly specialized communication and coherence among tissue clocks is rewired by nutrient challenge. Overall, we illustrate how dynamic metabolic relationships can be reconstructed across time and space and how integration of circadian metabolomics data from multiple tissues can improve our understanding of health and disease.

Reprogramming of the circadian clock by nutritional challenge

Circadian rhythms and cellular metabolism are intimately linked. Here, we reveal that a high-fat diet (HFD) generates a profound reorganization of specific metabolic pathways, leading to widespread remodeling of the liver clock. Strikingly, in addition to disrupting the normal circadian cycle, HFD causes an unexpectedly large-scale genesis of de novo oscillating transcripts, resulting in reorganization of the coordinated oscillations between coherent transcripts and metabolites. The mechanisms underlying this reprogramming involve both the impairment of CLOCK:BMAL1 chromatin recruitment and a pronounced cyclic activation of surrogate pathways through the transcriptional regulator PPARγ. Finally, we demonstrate that it is specifically the nutritional challenge, and not the development of obesity, that causes the reprogramming of the clock and that the effects of the diet on the clock are reversible.

Methods for the analysis of the sperm proteome

Proteomics is the study of the proteins of cells or tissues. Sperm proteomics aims at the identification of the proteins that compose the sperm cell and the study of their function. The recent developments in mass spectrometry (MS) have markedly increased the throughput for the identification and study of the sperm proteins. Catalogues of spermatozoal proteins in human and in model species are becoming available laying the groundwork for subsequent research, diagnostic applications, and the development of patient-specific treatments. A wide range of MS techniques is also rapidly becoming available for researchers. This chapter describes a methodological option to study the sperm cell using MS and provides a detailed protocol to identify the proteins extracted from a Percoll-purified human sperm population and separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) using LC-MS/MS.

Circadian proteins CLOCK and BMAL1 in the chromatoid body, a RNA processing granule of male germ cells

Spermatogenesis is a complex differentiation process that involves genetic and epigenetic regulation, sophisticated hormonal control, and extensive structural changes in male germ cells. RNA nuclear and cytoplasmic bodies appear to be critical for the progress of spermatogenesis. The chromatoid body (CB) is a cytoplasmic organelle playing an important role in RNA post-transcriptional and translation regulation during the late steps of germ cell differentiation. The CB is also important for fertility determination since mutations of genes encoding its components cause infertility by spermatogenesis arrest. Targeted ablation of the Bmal1 and Clock genes, which encode central regulators of the circadian clock also result in fertility defects caused by problems other than spermatogenesis alterations. We show that the circadian proteins CLOCK and BMAL1 are localized in the CB in a stage-specific manner of germ cells. Both BMAL1 and CLOCK proteins physically interact with the ATP-dependent DEAD-box RNA helicase MVH (mouse VASA homolog), a hallmark component of the CB. BMAL1 is differentially expressed during the spermatogenic cycle of seminiferous tubules, and Bmal1 and Clock deficient mice display significant CB morphological alterations due to BMAL1 ablation or low expression. These findings suggest that both BMAL1 and CLOCK contribute to CB assembly and physiology, raising questions on the role of the circadian clock in reproduction and on the molecular function that CLOCK and BMAL1 could potentially have in the CB assembly and physiology.

Protamine 2 precursors and processing

Protamine 2 (P2) is synthesised as a precursor protein (pre-P2) which by proteolysis is processed to generate the mature components of the protamine 2 family of proteins (HP2, HP3 and HP4). In infertile patients, abnormal processing of the protamine 2 precursors has been suggested by the detection of an increased presence of precursor forms. However, the presence of small detectable amounts of precursor proteins has been demonstrated also in normal sperm samples, although the variation of pre-P2 in individual human sperm cells had not yet been explored. In the present manuscript we perform a mini-review describing what is known about protamine 2 precursors and P2 processing. In addition, we by immunofluorescence demonstrate the existence of a marked variation in the presence and abundance of pre-P2 in individual sperm cells.

Proteomic characterization of the human sperm nucleus

Generating a catalogue of sperm nuclear proteins is an important first step towards the clarification of the function of the paternal chromatin transmitted to the oocyte upon fertilization. With this goal, sperm nuclei were obtained through CTAB treatment and isolated to over 99.9% purity without any tail fragments, acrosome or mitochondria as assessed by optical microscopy and transmission electron microscopy. The nuclear proteins were extracted and separated in 2-D and 1-D gels and the 2-D spots and 1-D bands were excised and analysed to identify the proteins through LC-MS/MS. With this approach, 403 different proteins have been identified from the isolated sperm nuclei. The most abundant family of proteins identified are the histones, for which several novel members had not been reported previously as present in the spermatogenic cell line or in the human mature spermatozoa. More than half (52.6%) of the proteins had not been detected in the previous human whole sperm cell proteome reports. Of relevance, several chromatin-related proteins, such as zinc fingers and transcription factors, so far not known to be associated with the sperm chromatin, have also been detected. This provides additional information about the nuclear proteins that are potentially relevant for epigenetic marking, proper fertilization and embryo development.

Identification of proteomic differences in asthenozoospermic sperm samples

BACKGROUND

Asthenozoospermia is one of the most common findings present in infertile males, but its aetiology remains unknown in most cases. Present proteomic tools now offer the opportunity to identify proteins which are differentially expressed in asthenozoospermic semen samples and potentially involved in infertility.

METHODS

We compared the expression of 101 sperm protein spots in 20 asthenozoospermic samples to that of 10 semen donor controls using two-dimensional proteomic analysis.

RESULTS

Seventeen protein spots have been identified at different amounts in the asthenozoospermic samples compared with controls. These are cytoskeletal actin-B, annexin-A5, cytochrome C oxidase-6B, histone H2A, prolactin-inducible protein and precursor, calcium binding protein-S100A9 (2 spots), clusterin precursor, dihydrolipoamide dehydrogenase precursor, fumarate hydratase precursor, heat shock protein-HSPA2, inositol-1 monophosphatase, 3-mercapto-pyruvate sulfurtransferase/dienoyl-CoA isomerase precursor, proteasome subunit-PSMB3, semenogelin 1 precursor and testis expressed sequence 12. The detected amount of these proteins enabled the grouping of asthenozoospermic sperm samples in an unsupervised clustering analysis.

CONCLUSIONS

We have identified several proteins present at different amount in asthenozoospermic sperm samples. These proteins could be candidates towards the development of diagnostic markers, and open up the opportunity to gain further insight into the pathogenic mechanisms involved in asthenozoospermia.

Proteomics of human spermatozoa, protamine content and assisted reproduction outcome

It is well known that alterations in the expression of the major sperm nuclear proteins (protamines) are related to infertility in man. In addition, other minor proteins extracted from human spermatozoa are being analysed by 2-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and identified by MALDI-TOF MS analysis. The function of the identified proteins turns out to be energy production, transcription, protein synthesis, transport, folding and turnover, cell cycle, apoptosis and oxidative stress, signal transduction, cytoskeleton, flagella and cell movement, cell recognition, metabolism and unknown function. Many of the proteins identified using MALDI-TOF had not been yet been described as being expressed in human spermatozoa. Substantial differences have been detected in the levels of some of the newly identified human sperm proteins in the different groups of infertile patients. Present research efforts are targeting the potential correlations among changes in the proteomic composition, protamine content, DNA integrity and assisted reproduction outcome.