{"id":7930,"date":"2025-09-25T09:35:20","date_gmt":"2025-09-25T09:35:20","guid":{"rendered":"https:\/\/neuropediatoolkit.org\/?p=7930"},"modified":"2026-09-24T15:28:05","modified_gmt":"2026-09-24T15:28:05","slug":"arx-gene","status":"publish","type":"post","link":"https:\/\/neuropediatoolkit.org\/en\/arx-gene\/","title":{"rendered":"ARX \u200b\u200bgen."},"content":{"rendered":"<p class=\"wp-block-paragraph\">The gene <em>ARX<\/em> (Aristaless-related homeobox), located on chromosome<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Molecular Basis and Pathogenic Mechanisms<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The ARX protein contains a homeodomain domain at its N-terminus, essential for DNA binding and regulation of target genes. In addition, it has a domain of alanine repeats (poly-alanine repeats) in its central region, whose normal length ranges between 10 and 13 repeats. The mutations in <em>ARX<\/em> They can be of two main types:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Loss-of-function mutations, such as deletions, frameshift insertions, or nonsense mutations, that reduce or eliminate the activity of the protein. <\/li>\n\n\n\n<li>Gain-of-function mutations, especially those that increase the number of polyalanine repeats (e.g., 16 or more repeats), which alter the three-dimensional conformation of the protein and its ability to interact with cofactors.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This latter mechanism is particularly associated with Partington syndrome and X-linked familial lissencephaly, where the overpresence of polyalanine repeats alters the regulation of genes involved in neuronal migration, causing a disruption of the cortical architecture.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Clinical Spectrum: From Lissencephaly to Neonatal Epilepsy<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The phenotypic spectrum associated with the gene <em>ARX<\/em> It is one of the broadest and most complex in neurogenetics. Although it was initially described as a gene involved in X-linked familial lissencephaly (X-linked lissencephaly with abnormal genitalia, XLAG), its range of clinical manifestations ranges from mild disorders to fatal forms. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>X-linked familial lissencephaly<\/strong> It is characterized by an almost total absence of brain folds (lissencephaly), with a thick and smooth cortex, accompanied by genital anomalies (testicular hypoplasia, absence of M\u00fcllerian ducts) and a progressive neurodegenerative evolution. Patients usually present with spastic paralysis, global developmental delay, and generalized epilepsy from birth, often resistant to multiple antiepileptics.<\/li>\n\n\n\n<li>In contrast, the <strong>Partington syndrome<\/strong> It is associated with specific mutations in the polyalanine repeat domain, usually with an excessive number of repeats (e.g., 16-20). This syndrome is clinically manifested by the association of a mild to moderate intellectual deficit, dysarthria, and dystonic hand movements. <\/li>\n\n\n\n<li>The <strong>West syndrome<\/strong> is also strongly associated with mutations in <em>ARX<\/em>. In this context, the syndrome presents as a form of early epileptic encephalopathy, with the classic triangle: flexion spasms (hyperextension), encephalopathy with disorganized activation pattern on EEG (better known as <em>hypsarrhythmia<\/em>), and developmental delay. <\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Diagnosis and Technical Challenges<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The diagnosis of disorders due to mutations in <em>ARX<\/em> requires an advanced diagnostic strategy. Although exome sequencing is a powerful tool, its sensitivity for detecting polyalanine repeats or large deletions is limited. In this sense, the EuroEPINOMICS article highlights that the gene <em>ARX<\/em> it's a <strong>paradigmatic example of a gene that can escape exome sequencing <\/strong>standard due to its repetitive structure and the presence of regions with high homology that make precise alignment difficult. Therefore, it is recommended to complement the exome with techniques such as PCR with repeat amplification, analysis of DNA fragments (for example, with capillary electrophoresis), or even long-read sequencing (such as PacBio or Oxford Nanopore) to detect complex structural variations.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"765\" src=\"https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1024x765.png\" alt=\"Espectro fenot\u00edpico de mutaciones en ARX\" class=\"wp-image-7931\" srcset=\"https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1024x765.png 1024w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-300x224.png 300w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-768x574.png 768w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-16x12.png 16w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image.png 1484w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img decoding=\"async\" width=\"667\" height=\"437\" src=\"https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1.png\" alt=\"Mecanismos patog\u00e9nicos de las mutaciones en ARX\" class=\"wp-image-7932\" srcset=\"https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1.png 667w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1-300x197.png 300w, https:\/\/neuropediatoolkit.org\/wp-content\/uploads\/2025\/09\/image-1-18x12.png 18w\" sizes=\"(max-width: 667px) 100vw, 667px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-embed is-type-wp-embed is-provider-beyond-the-ion-channel wp-block-embed-beyond-the-ion-channel\">\n<div class=\"wp-block-embed__wrapper\">\n  <a href=\"https:\/\/epilepsygenetics.blog\/arx-this-is-what-you-need-to-know\/\">https:\/\/epilepsygenetics.blog\/arx-this-is-what-you-need-to-know\/<\/a>\n<\/div>\n<\/figure>\n\n\n\n<figure class=\"wp-block-embed is-type-wp-embed is-provider-beyond-the-ion-channel wp-block-embed-beyond-the-ion-channel\">\n<div class=\"wp-block-embed__wrapper\">\n  <a href=\"https:\/\/euroepinomics.wordpress.com\/2014\/05\/19\/the-arx-problem-how-an-epilepsy-gene-escapes-exome-sequencing\/\">https:\/\/euroepinomics.wordpress.com\/2014\/05\/19\/the-arx-problem-how-an-epilepsy-gene-escapes-exome-sequencing\/<\/a>\n<\/div>\n<\/figure>","protected":false},"excerpt":{"rendered":"<p>The ARX (Aristaless-related homeobox) gene, located on chromosome Molecular Basis and Pathogenic Mechanisms The ARX protein contains a\u2026 <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/neuropediatoolkit.org\/en\/arx-gene\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> \u00abARX gene.\u00bb<\/span><\/a><\/p>","protected":false},"author":1,"featured_media":7931,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_themeisle_gutenberg_block_has_review":false,"footnotes":""},"categories":[4,10],"tags":[],"class_list":["post-7930","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-epilepsia","category-neurogenetica","entry"],"_links":{"self":[{"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/posts\/7930","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/comments?post=7930"}],"version-history":[{"count":3,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/posts\/7930\/revisions"}],"predecessor-version":[{"id":8721,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/posts\/7930\/revisions\/8721"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/media\/7931"}],"wp:attachment":[{"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/media?parent=7930"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/categories?post=7930"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/neuropediatoolkit.org\/en\/wp-json\/wp\/v2\/tags?post=7930"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}