CASE REPORT: HUMAN DIGASTRIC SARTORIUS MUSCLE WITH AN EVO‐DEVO APPROACH
Authors: Mondragon Edward Javier Acero , Baron Diego Mauricio Aldana , Dussan Maria Margarita , Villegas Andrea Lopez , Bendeck Joanna 
Published: June 2021

INTRODUCTION

Hox genes are essential in the fixation of the anteroposterior axes in symmetrical individuals. During mammal evolution of the musculoskeletal system's paired appendages there has been expresión HOX genes; for example, Tbx4 genes determine the identity of hind limbs when paired paraxial mesoderm originates hypaxial and epaxial muscles. From an ontogenetic perspective, muscle embryology has myogenic hierarchical control genes such as Myf5, MyoD, myogenin and MRF4, when linked with diversity controlling genes like Kdm5, Med13, Tcfap4 Atrophin1, Rere, Elongin‐B, ZBTB20, AF10/AF17, Kdm2, Sin3A justify muscular morphological diversity, loss or duplication. Once this is understood trough an evolutionary perspective, one may understand sartorius muscle diversity in mammals. In the case of ruminants, this muscle has a morphology with two superior heads. Interestingly enough, the same sartorius morphology has been documented in humans like an anatomical variant. The present case aims to describe this anatomical variant with an EVO‐DEVO approach.

REPORT CASE

During the course of a second year anatomy class, at La Universidad de La Sabana, the class professor, when exploring the corpse of a 40 year old male, noticed a digastric belly sartorius muscle on the left lower limb, while also noticing an uncommonly thick sartorium on the right lower limb. [Figure 1]. When it came to the digastric sartorius muscle, both bellies ran parallel to each another, however they were covered by different fascia. The medial head originated from the superior border of the anterior superior iliac crest. The lateral head had its classical origin. Both heads had the classical muscular insertion.

Discussion

In natural populations, there are reports of morphological left – right differences, however, reports of individuals with asymmetric morphologies are rare, suggesting the possibility that asymmetric individuals might arise as a result of imperfect development. This may be reflected by the genome's instability due to interactions with environmental factors or “noise”. The stability of the genome is an intrinsic capacity of an organism to resist external disturbances that may occur during natural development and growth. In this case report, the obvious sartorius muscles asymmetry is evidence that invites us to consider the Evo‐Devo perspective. Such idea suggests the possibility that any disturbance during early ontogeny of the lower limb might have occurred as consequence of the genome's lack of buffer capacity. This reminds us, that myogenic control and diversity genes define an individual's symmetry when they are buffered.

Conclusion

A molecular Evo‐Devo approach should be started in ontogenical manner in order to explain the asymmetry cases that might be found.

Support or Funding Information

PROSEIM

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.