El lunes y martes 20 y 21 de noviembre coordinamos un simposio internacional en la Fundación Ramón Areces, sobre los defectos del transporte de aminoácidos.

1. Role of LAT2
in
Age-Related Hearing Loss
by Meritxell Espino Guarch Ph.D.
Immunology & Inflammation
Translational Medicine
20thNovember 2017

2. 1982
2014
2009
2004
2009
Academic Medical Center
for
Women & Children
Qatar, Doha

3. Active transport across plasmatic membrane
Heavy chain
Light chain
Heteromeric Amino acid Transporters (HATs)
Introduction

4. HATs
Fernández et al. Biochem. J 2000
Putative role of LAT2 in transepithelial flux of cystine
Introduction

5. LAT2
Lat2 Knockout generation
LAT2 expression in basolateral membranes
LAT2 Ab against C-term
Done by M.Font-Llitjós
Injection & Chimera Generation
Done by Genoway
Kidney = Brain = Placenta = Intestine > Stomach > Pancreas > Spleen = Eye >
Sk. Muscle >> > Lung = Heart = Liver
Results

6. Plasma & urine
amino acid content
Plasma(mM)
Urine(nmolsAA/24h·g)
Renal Phenotype
Results

7. Absortion Phenotype
Results
Hypophysis

8. Apical dendrites
and synaptic area
Preoptic area fibers
Pituitary gland
Blood vessel
Subfornical organ
Choroid plexus
LAT2 localization in brain
Results

9. Behavior Studies
Done by M.Font-Llitjós & I. Sahún
Pre-Pulse Inhibition Test
Results

10. Stress Response
Restrain stress
Hypophysis
Results
Auditory Brainstem Response (ABR)
hypoacusis
402816 208
0
25
50
75
100
Threshold(dBSPL)
***
Frequency (KHz)
Wild type
Heterozygous
LAT2 Knockout
Done by S. Murillo

11. LAT2 expression in cochlea
Results
Sanchez-Calderon et al. 2010

12. Cochlear damage
Results
Spiral ligament (role in cochlea homeostasis)
LAT2 is expressed in Fibrocytes
Done by A. Celaya
Stria vascularis (role in maintenance of the
endocochlear potential)
WildtypeLAT2-/-
*
Alterations in SL could affect SV

13. Results
Spiral ganglia Hair Cells
(Organ of Corti)
WildtypeLAT2-/-
0 50 100
% Epithelia Integrity
Wild Type
Hetero
Lat2KO
0 25 50 75 100
0
2500
5000
7500
10000
% of Intact Epithelia
SGNNuclei/mm2

14. Hearing Loss Penetrance
Done by S. Murillo
Results
LAT2 through aging
2-months old
12-months old
Done by A. Celaya

15. Patients Screening
Done by D. Vuckovic and G. Girotto
147 individuals from isolated villages in Italy >50-year old
Inclusion criteria for ARHL
high frequencies (PTA-H) > 40 dB
Results
Chr. 14 Variant Consequence Code
Frequency
Esp6500siv2 1000g Campion ExAC
Studied
Cohort
23597290 14:23597291 C / T p.Val460Glu V460E NA NA 0.0013 0.00002475 0.015
23598917 14:23598917 G / A p.Thr402Met T402M NA NA 0.0047 0.00002471 0.015
23608641
14:23608641 C / T
(rs142951280)
p.Val302Ile V302I 0.0005 NA 0.0047 0.0004613 0.015
23598870 14:23598869 C / T p.Arg418Cys R418C 0.0005 NA 0.002 0.00002477 0.015
23652101
14:23652101 C / G
(rs141772308)
p.Arg8Pro R8P 0.0008 NA 0.0013 0.0008156 0.012
23635621
14:23635621 C / T
(rs139927895)
p.Ala94Thr A94T 0.0012 0.002 0.0013 0.00202 0.012
23612368
14:23612368 C / T
(rs149245114)
p.Arg185Leu R185L NA NA 0.002 0.00002471 0.012

16. Location of the mutations
Results
Conservate AA
Inward-facing lid
T<M delate H-H
interactions with
the substrate
Based on the homologous protein AdiC

17. In vitro studies
Done by E. Errasti-Murugarren
Results
ARHL Controls
LAT2
DAPI
MB-marker

18. Conclusion
Loss-of-function of LAT2 is associated with ARHL in both humans and mice
Hearing loss severity increases with age in heterozygous and Lat2-/- mice
LAT2 expression in cochlea rises during ageing
4 novel mutations in LAT2 had been identified in ARHL
V460E, T402M, V302I and R418C
Variants showed loss-of-function of transport substrate-dependent
Full LAT2 function is needed to keep optimal hearing function throughout life, with half a dose
of LAT2 being enough to accelerate ARHL phenotype in mice and humans

19. How LAT2 lost-of-function affects cochlear function?
Lack of LAT2 affects hearing
SENSORY (Hair Cells)
NEURAL (Spiral Ganglia)
METABOLIC (Stria Vascularis)
LAT2 transports
Neutral AA (except proline)
L-DOPA (protective role in cochlea during aging)
Thyroid Hormones (hypothyroidism affects cochlea development)
Unresolved chronic inflammation in Lat2 knockout cochlea
Active-macrophages marker

20. Virgina Nunes Lab
Manuel Palacín Lab
Mara Dierssen Lab
Working on
the manuscript
Paolo Gasparini Lab
Isabel Varela-Nieto Lab
HATs
Mouse
Behavior
Cochlea
Humans

21. Results

22. Done by S. Murillo
Results