Neuronal Delamination and Outer Radial Glia Generation in Neocortical Development

During neocortical development, many neuronally differentiating cells (neurons and intermediate progenitor cells) are generated at the apical/ventricular surface by the division of neural progenitor cells (apical radial glial cells, aRGs). Neurogenic cell delamination, in which these neuronally differentiating cells retract their apical processes and depart from the apical surface, is the first step of their migration. Since the microenvironment established by the apical endfeet is crucial for maintaining neuroepithelial (NE)/aRGs, proper timing of the detachment of the apical endfeet is critical for the quantitative control of neurogenesis in cerebral development. During delamination, the microtubule-actin-AJ (adherens junction) configuration at the apical endfeet shows dynamic changes, concurrent with the constriction of the AJ ring at the apical endfeet and downregulation of cadherin expression. This process is mediated by transcriptional suppression of AJ-related molecules and multiple cascades to regulate cell adhesion and cytoskeletal architecture in a posttranscriptional manner. Recent advances have added molecules to the latter category: the interphase centrosome protein AKNA affects microtubule dynamics to destabilize the microtubule-actin-AJ complex, and the microtubule-associated protein Lzts1 inhibits microtubule assembly and activates actomyosin systems at the apical endfeet of differentiating cells. Moreover, Lzts1 induces the oblique division of aRGs, and loss of Lzts1 reduces the generation of outer radial glia (oRGs, also called basal radial glia, bRGs), another type of neural progenitor cell in the subventricular zone. These findings suggest that neurogenic cell delamination, and in some cases oRG generation, could be caused by a spectrum of interlinked mechanisms.

The association of AKNA gene polymorphisms with knee osteoarthritis suggests the relevance of this immune response regulator in the disease genetic susceptibility

Recent studies have identified AKNA as a potential susceptibility gene for several inflammatory diseases. Here, we aimed to assess the potential association of AKNA polymorphisms with knee osteoarthritis (KOA) susceptibility in a Mexican population, following STREGA recommendations. From a DNA bank of 181 KOA patients and 140 healthy controls, two AKNA SNPs were genotyped using TaqMan probes. The association between KOA susceptibility and AKNA polymorphisms genotypes was evaluated by multivariated logistic regression analysis. Information regarding patients' inflammatory biomarkers levels was obtained and their association with AKNA polymorphisms genotypes was assessed by lineal regression. We found a positive association with the recessive inheritance model of both AKNA polymorphisms (A/A genotype for both) and KOA susceptibility adjusting by age, body mass index (BMI), gender and place of birth (OR = 2.48, 95% CI 1.09-5.65 for rs10817595 polymorphism; and OR = 4.96; 95% CI 2.421-10.2 for rs3748176 polymorphism). Additionally these associations were also seen after stratifying patients by KOA severity and age. Furthermore the total leukocyte count was positively associated with rs10817595 AKNA polymorphism (β = 1.39; 95% CI 0.44-2.34) adjusting by age, BMI, gender, place of birth and disease severity. We suggest that regulatory and coding polymorphisms of the inflammatory modulator gene AKNA can influence the development of KOA. Further structural and functional studies might reveal the role of AKNA in OA and other rheumatic diseases.

Functional Role of AKNA: A Scoping Review

Human akna encodes an AT-hook transcription factor whose expression participates in various cellular processes. We conducted a scoping review on the literature regarding the functional role of AKNA according to the evidence found in human and in vivo and in vitro models, stringently following the "PRISMA-ScR" statement recommendations.

METHODS

We undertook an independent PubMed literature search using the following search terms, AKNA OR AKNA ADJ gene OR AKNA protein, human OR AKNA ADJ functions. Observational and experimental articles were considered. The selected studies were categorized using a pre-determined data extraction form. A narrative summary of the evidence was produced.

RESULTS

AKNA modulates the expression of CD40 and CD40L genes in immune system cells. It is a negative regulator of inflammatory processes as evidenced by knockout mouse models and observational studies for several autoimmune and inflammatory diseases. Furthermore, AKNA contributes to the de-regulation of the immune system in cancer, and it has been proposed as a susceptibility genetic factor and biomarker in CC, GC, and HNSCC. Finally, AKNA regulates neurogenesis by destabilizing the microtubules dynamics.

CONCLUSION

Our results provide evidence for the role of AKNA in various cellular processes, including immune response, inflammation, development, cancer, autoimmunity, and neurogenesis.

The Human Papillomavirus (HPV) E6 Oncoprotein Regulates CD40 Expression via the AT-Hook Transcription Factor AKNA

Persistent infection with high-risk Human Papillomavirus (HR-HPV) is the main requisite for cervical cancer development. Normally, HPV is limited to the site of infection and regulates a plethora of cellular elements to avoid the immune surveillance by inducing an anti-inflammatory state, allowing the progress through the viral cycle and the carcinogenic process. Recent findings suggest that the AT-hook transcriptional factor AKNA could play a role in the development of cervical cancer. AKNA is strongly related to the expression of co-stimulatory molecules such CD40/CD40L to achieve an anti-tumoral immune response. To date, there is no evidence demonstrating the effect of the HPV E6 oncoprotein on the AT-hook factor AKNA. In this work, minimal expression of AKNA in cervical carcinoma compared to normal tissue was found. We show the ability of E6 from high-risk HPVs 16 and 18 to interact with and down-regulate AKNA as well as its co-stimulatory molecule CD40 in a proteasome dependent manner. We also found that p53 interacts with AKNA and promotes AKNA expression. Our results indicate that the de-regulation of CD40 and AKNA is induced by the HPV E6 oncoprotein, and this event involves the action of p53 suggesting that the axis E6/p53A/AKNA might play an important role in the de-regulation of the immune system during the carcinogenic process induced by HR-HPV.

A Homozygous AKNA Frameshift Variant Is Associated with Microcephaly in a Pakistani Family

Primary microcephaly (MCPH) is a prenatal condition of small brain size with a varying degree of intellectual disability. It is a heterogeneous genetic disorder with 28 associated genes reported so far. Most of these genes encode centrosomal proteins. Recently, AKNA was recognized as a novel centrosomal protein that regulates neurogenesis via microtubule organization, making AKNA a likely candidate gene for MCPH. Using linkage analysis and whole-exome sequencing, we found a frameshift variant in exon 12 of AKNA (NM_030767.4: c.2737delG) that cosegregates with microcephaly, mild intellectual disability and speech impairment in a consanguineous family from Pakistan. This variant is predicted to result in a protein with a truncated C-terminus (p.(Glu913Argfs*42)), which has been shown to be indispensable to AKNA’s localization to the centrosome and a normal brain development. Moreover, the amino acid sequence is altered from the beginning of the second of the two PEST domains, which are rich in proline (P), glutamic acid (E), serine (S), and threonine (T) and common to rapidly degraded proteins. An impaired function of the PEST domains may affect the intracellular half-life of the protein. Our genetic findings compellingly substantiate the predicted candidacy, based on its newly ascribed functional features, of the multifaceted protein AKNA for association with MCPH.

Binding to the Other Side: The AT-Hook DNA-Binding Domain Allows Nuclear Factors to Exploit the DNA Minor Groove

The "AT-hook" is a peculiar DNA-binding domain that interacts with DNA in the minor groove in correspondence to AT-rich sequences. This domain has been first described in the HMGA protein family of architectural factors and later in various transcription factors and chromatin proteins, often in association with major groove DNA-binding domains. In this review, using a literature search, we identified about one hundred AT-hook-containing proteins, mainly chromatin proteins and transcription factors. After considering the prototypes of AT-hook-containing proteins, the HMGA family, we review those that have been studied in more detail and that have been involved in various pathologies with a particular focus on cancer. This review shows that the AT-hook is a domain that gives proteins not only the ability to interact with DNA but also with RNA and proteins. This domain can have enzymatic activity and can influence the activity of the major groove DNA-binding domain and chromatin docking modules when present, and its activity can be modulated by post-translational modifications. Future research on the function of AT-hook-containing proteins will allow us to better decipher their function and contribution to the different pathologies and to eventually uncover their mutual influences.

Identification of AKNA Gene and Its Role for Genetic Susceptibility in Epithelial Ovarian Cancer

AKNA is identified as a gene that regulates inflammation, immune response, and Epithelial-Mesenchymal Transition (EMT), which plays an important role in the progression of epithelial ovarian cancer. In this study, we analyzed the genotype and allele distribution as well as 3D modeling of one of the AKNA rs10817595 (-1372 C>A). The distribution of genotypes and alleles was analyzed using the T-ARMS PCR method on 63 ovarian cancer samples and 65 controls. AKNA mRNA expression was analyzed using qRT-PCR on 35 low-grade and 28 high-grade samples. Fifteen low-grade and 12 high-grade samples were analyzed for AKNA protein levels using immunohistochemistry. A 3D model of protein structure was constructed using AlphaFold. Significant differences in AKNA protein levels were found. However, no significant correlation was found for relative AKNA mRNA expression with protein levels. This result is thought to be related to decreased immune system response, increased inflammation, and increased EMT in epithelial ovarian cancer. AKNA gene variant (-1372 C>A) can cause a decrease in mRNA and protein levels in the low-grade and high-grade groups, so it has the potential as a genetic susceptibility factor in epithelial ovarian cancer.

Critical Role of the Transcription Factor AKNA in T-Cell Activation: An Integrative Bioinformatics Approach

The human akna gene encodes an AT-hook transcription factor, the expression of which is involved in various cellular processes. The goal of this study was to identify potential AKNA binding sites in genes that participate in T-cell activation and validate selected genes. Here we analyzed ChIP-seq and microarray assays to determine AKNA-binding motifs and the cellular process altered by AKNA in T-cell lymphocytes. In addition, we performed a validation analysis by RT-qPCR to assess AKNA's role in promoting IL-2 and CD80 expression. We found five AT-rich motifs that are potential candidates as AKNA response elements. We identified these AT-rich motifs in promoter regions of more than a thousand genes in activated T-cells, and demonstrated that AKNA induces the expression of genes involved in helper T-cell activation, such as IL-2. The genomic enrichment and prediction of AT-rich motif analyses demonstrated that AKNA is a transcription factor that can potentially modulate gene expression by recognizing AT-rich motifs in a plethora of genes that are involved in different molecular pathways and processes. Among the cellular processes activated by AT-rich genes, we found inflammatory pathways potentially regulated by AKNA, suggesting AKNA is acting as a master regulator during T-cell activation.